Should a professor recommending me talk about my (bad) grades in his or her letter? I recently graduated with a bachelor's degree in economics. I'm now applying to research internships and some of these need recommendation letters from faculty. 

I did very badly during the first 2 years at college (having scored around 6/10 (=2.4/4) GPA in my courses until the end of my 4th semester) -- however, I learnt from my mistakes and became much more disciplined in my 3rd year, when I scored an average of 8/10 (3.2/4). At the end of 3 years, I had to graduate with a sub-3 CGPA of 6.88/10 (2.75/4). 

I did really well on research projects and other quantitative projects at college, which is one reason why I've found professors to recommend me. I understand that my poor GPA will probably put me in a bad position, but what's done is done and I digress. One of my possible references asked me to draft a letter for him and that he will make changes as necessary before sending it in.

My question is: should I ask my references to talk about my poor grades (something along the lines of "While X does not have impressive scores in his undergraduate degree, it can be clearly seen from his transcripts that he picked up pace and discipline during his final year. I believe that X has taken home the importance of hardwork after a few hiccups in his academic life".)

Even if the above phrasing doesn't seem good, in general, is it a good idea to talk about your bad grades in a recommendation letter? Or is it simply better to let this go and concentrate on my strengths?
It really depends on how the professor knows you.

If the professor only knew you "after the change", the letter might say "I am aware of student's relatively low grades during the first few years, but by the time of my class, they were a top-performing student", that kind of thing.  

If the professor has known you for years, it might be appropriate to comment on having observed this change, and expressing confidence that you can handle the role in question despite the low cumulative QPA.