user985: Suppose a monk is invited to a house for food and the lay person asks how the food is? How does a monk reply to such a question. I am sure a monk in his lifetime comes across many such subjective questions. How should he deal with them? Does he:

Just reply something to satisfy the lay person
Give him/her a teaching on impermanence of everything

From the stories in Buddha's life, it is clear that he laid great emphasis on timing his teachings to someone. Many a time he would say that this is not the right time for him/her to learn the Dhamma. Having this in context, does it make sense to impart teaching at every possible opportunity.
Please incorporate any stories if any to showcase the tradition. 

user295: Though not directly related to Buddhism "How to speak so that people want to listen" gives a good strategy to be used in such situation. It is:

Being truthful coupled with
Compassion

And not being blunt though trueful. In this cases you can be very tactful like answering question like was the food good, etc.

user-1: My Guru said that if she was eating in someone's home and they put non-vegetarian food in front of her, not knowing she had chosen to not eat meat, she would eat anyway and be grateful for the gift of care and attention the person had made. She did not say (as far as I know) how to answer directly such a question as you asked, but I would say: 1) express pleasure if you enjoy the food 2) express gratitude and whatever you can politely say otherwise, only if asked. I think this is normal common sense, and applies to Monks as well. I can usually find something nice to say about any meal. It is good training for not being so picky, so eat out as much as you can!

user254: 
Please incorporate any stories if any to showcase the tradition

I cannot say what a monk should do, so this answer is off-topic, and theoretical, for what it's worth.
I had e.g. here a very small amount of insight into conversation when there's a disjoint view of reality.
You might be worried that because the monk and the host have a different view/insight about the food, therefore it's not a topic/subject which they can share a conversation about.
I'd suggest that the 'monk' might try to react/respond to the person, not to the food. Perhaps something like, "It's kind of you to invite me" or "It's kind of you to care about my welfare" or just "It's good" ... and then try to reciprocate, perhaps inquire after the welfare of the person you're talking to.
Also my mum taught pre-schoolers. Part of her advice for controlling their behaviour was, instead of scolding them for bad behaviour, wait until they show some good behaviour and praise that. So you might not want to be scolding a layperson about impermanence. In fact the book described in this answer was written by a monk who deals with laypeople in Texas: and it claims, explicitly, that "impermanence" and "dukkha" and so on are concepts which were more intended for monks than for laypeople.

Please incorporate any stories if any to showcase the tradition
Here's one Zen story that could be relevant to what I was saying above:
No Loving-Kindness

"To think I fed that fellow for twenty years!" exclaimed the old woman in anger. "He showed no consideration for your needs, no disposition to explain your condition. He need not have responded to passion, but at least he should have evidenced some compassion."

I think a moral of that story is, 'Loving-kindness: don't leave home without it.'
An article like Detachment and Compassion might be apposite.

Here is another:

Brother Stream handed out clementines and we all learnt how to peel and eat the fruit slowly and mindfully, enjoying the bright orange colour, the citrus fragrance and the crisp sound as we each held a Clementine up to our ear and gently removed the peel in one long piece, before holding a segment in our mouths and enjoying the taste.

This one is a bit different:

It's with school-children
Eating is just one activity (read the article for the 'bell' before eating and the 'singing' afterwards)


user755: Being attached to some rule about how to answer certain questions isn't the point.
Good answers come out of being present and aware.
The same question will be answered differently at different moments depending on what the moment calls for.
"Every possible opportunity" is an interesting phrase. If someone isn't ready to learn something there no opportunity to teach him something. Being a good teacher means to know what someone can learn and then give him that lesson. It's not about throwing a lot of spaghetti on the wall and hoping that something sticks.
Christian missionaries do thing that it's the intention that counts. Christian missionaries will lecture someone whether or not there an opportunity to teach something. For them the act in itself is important.
Buddhism is different. It's about being skillful and only teach when the student can learn. Teaching requires patience and waiting for a possible opportunity.

985: <p>Suppose a monk is invited to a house for food and the lay person asks how the food is? How does a monk reply to such a question. I am sure a monk in his lifetime comes across many such subjective questions. How should he deal with them? Does he:</p>

<ol>
<li>Just reply something to satisfy the lay person</li>
<li>Give him/her a teaching on impermanence of everything</li>
</ol>

<p>From the stories in Buddha's life, it is clear that he laid great emphasis on timing his teachings to someone. Many a time he would say that this is not the right time for him/her to learn the Dhamma. Having this in context, does it make sense to impart teaching at every possible opportunity.</p>

<p>Please incorporate any stories if any to showcase the tradition. </p>
 295: <p>Though not directly related to Buddhism "<a href="http://www.ted.com/talks/julian_treasure_how_to_speak_so_that_people_want_to_listen" rel="nofollow">How to speak so that people want to listen</a>" gives a good strategy to be used in such situation. It is:</p>

<ul>
<li>Being truthful coupled with</li>
<li>Compassion</li>
</ul>

<p>And not being blunt though trueful. In this cases you can be very tactful like answering question like was the food good, etc.</p>
 -1: <p>My Guru said that if she was eating in someone's home and they put non-vegetarian food in front of her, not knowing she had chosen to not eat meat, she would eat anyway and be grateful for the gift of care and attention the person had made. She did not say (as far as I know) how to answer directly such a question as you asked, but I would say: 1) express pleasure if you enjoy the food 2) express gratitude and whatever you can politely say otherwise, only if asked. I think this is normal common sense, and applies to Monks as well. I can usually find something nice to say about any meal. It is good training for not being so picky, so eat out as much as you can!</p>
 254: <blockquote>
  <p>Please incorporate any stories if any to showcase the tradition</p>
</blockquote>

<p>I cannot say what a monk should do, so this answer is off-topic, and theoretical, for what it's worth.</p>

<p>I had <a href="https://buddhism.stackexchange.com/questions/4053/compassion-to-friends-stepping-in-vs-letting-them-learn-on-their-own/4054#comment5426_4074">e.g. here</a> a very small amount of insight into conversation when there's a disjoint view of reality.</p>

<p>You might be worried that because the monk and the host have a different view/insight about the food, therefore it's not a topic/subject which they can share a conversation about.</p>

<p>I'd suggest that the 'monk' might try to react/respond to the person, not to the food. Perhaps something like, "It's kind of you to invite me" or "It's kind of you to care about my welfare" or just "It's good" ... and then try to reciprocate, perhaps inquire after the welfare of the person you're talking to.</p>

<p>Also my mum taught pre-schoolers. Part of her advice for controlling their behaviour was, instead of scolding them for bad behaviour, wait until they show some good behaviour and praise that. So you might not want to be scolding a layperson about impermanence. In fact <a href="https://buddhism.stackexchange.com/a/5460/254">the book described in this answer</a> was written by a monk who deals with laypeople in Texas: and it claims, explicitly, that "impermanence" and "dukkha" and so on are concepts which were more intended for monks than for laypeople.</p>

<hr>

<p><em>Please incorporate any stories if any to showcase the tradition</em></p>

<p>Here's one Zen story that could be relevant to what I was saying above:</p>

<p><a href="http://www.ashidakim.com/zenkoans/6noloving-kindness.html" rel="nofollow noreferrer">No Loving-Kindness</a></p>

<blockquote>
  <p>"To think I fed that fellow for twenty years!" exclaimed the old woman in anger. "He showed no consideration for your needs, no disposition to explain your condition. He need not have responded to passion, but at least he should have evidenced some compassion."</p>
</blockquote>

<p>I think a moral of that story is, 'Loving-kindness: don't leave home without it.'</p>

<p>An article like <a href="http://www.accesstoinsight.org/lib/authors/harris/bl141.html" rel="nofollow noreferrer">Detachment and Compassion</a> might be apposite.</p>

<hr>

<p><a href="http://www.dharmaschool.co.uk/monks-and-nuns-from-thich-nhat-hanh-collective-in-plum-village-france-pay-our-school-a-special-visit/" rel="nofollow noreferrer">Here is another</a>:</p>

<blockquote>
  <p>Brother Stream handed out clementines and we all learnt how to peel and eat the fruit slowly and mindfully, enjoying the bright orange colour, the citrus fragrance and the crisp sound as we each held a Clementine up to our ear and gently removed the peel in one long piece, before holding a segment in our mouths and enjoying the taste.</p>
</blockquote>

<p>This one is a bit different:</p>

<ul>
<li>It's with school-children</li>
<li>Eating is just one activity (read the article for the 'bell' before eating and the 'singing' afterwards)</li>
</ul>
 755: <p>Being attached to some rule about how to answer certain questions isn't the point.
Good answers come out of being present and aware.</p>

<p>The same question will be answered differently at different moments depending on what the moment calls for.</p>

<p>"Every possible opportunity" is an interesting phrase. If someone isn't ready to learn something there no opportunity to teach him something. Being a good teacher means to know what someone can learn and then give him that lesson. It's not about throwing a lot of spaghetti on the wall and hoping that something sticks.</p>

<p>Christian missionaries do thing that it's the intention that counts. Christian missionaries will lecture someone whether or not there an opportunity to teach something. For them the act in itself is important.</p>

<p>Buddhism is different. It's about being skillful and only teach when the student can learn. Teaching requires patience and waiting for a possible opportunity.</p>
