Signed up for conference, having second thoughts My advisor suggested that I should sign up for a conference, which I did - I now have to give a 15 minute talk. 

However, the conference is taking place very far from me (+20 hour flight), and I am having second thoughts on whether I should go or not. Here are my thoughts:

Pro 


Meet new people/socialize
Present my work at a talk, instead of merely a poster session


Con


Conference is only 4 days, two ~20 hours flights are very exhausting
The audience are not completely aligned with my field, so I have to make my presentation simpler than what the work actually is
Will not learn things that I directly need for my research because of the audience (they are in geology and engineering, I'm in math)


Honestly, I don't feel like going because of the above list. But I am worried that


My advisor will think I'm being annoying by "backing" out
I can't say no now, since I have been given a talk


I would be very happy to hear your opinions on this matter. Maybe I am putting too much thought into this.
I'd like to add several items to your list of pros:


Dissemination. You will make your work known to a whole new field of possibly interested people. If you're going there, I presume there is an interesting application in sight. Possible follow-ups. Lots of opportunities. Interdisciplinary collaboration. To be avid and down-to-earth, lots of citations might await. :)
Presenting experience. The best way to improve your presentation skills is giving talks. This is a good opportunity.
Connections It's always good to get to know people in academia. You might need to send them a quick e-mail with a question on their area of expertise. You might one day be looking for a post-doc job and they might be offering one (even if it's a position for an applied mathematician in a geology department). You might find a good idea for an interdisciplinary research project and apply for a grant.
Learning new things Yes, you will learn new things listening to the other talks, even if it's a different field. You might find a new related problem that you can solve. You might learn more about the applicative background of the problem that you are studying. You might find an example that looks great in the introduction of your next paper.
Tourism. When will you be able to visit again that far-away country? True, you won't see much if you are stuck in a university or a conference center, but that's still a great life experience in my view. One of the parts I enjoy the most of the academic career is being able to travel and see the world.
Money availability. Your advisor says that there is money for the trip, this time. My advice is go for it. More troubled times might come in future.
Trust your advisor. (S)he suggested you to sign up, so he thinks it's a good idea for you to go. You should trust him, it's the person who best knows the conference, your work and your situation.


I've been doing some interdisciplinary research lately. It's hard at first, but fascinating and productive once you enter it. There is a big entry barrier in getting to know each other's field and learning to use the same language, but there are lots of interesting results to gather just by putting together the ideas and methods of two different fields.

EDIT: added "trust your advisor"