+2 million
I'm in a similar organization abroad, and it has made me a stronger person than I would've ever imagined. It sounds cheesy, but I have learned so much about people and life in general by living and working in my school and small community, trying to get students to learn English, really care about school and their future and pass their tests, and the list could go on. There is really a lot to learn through this experience.
However, as has been said previously, this is NOT a decision to take lightly. I went into my program because I have a passion for teaching and I was thinking about pursuing it as a career; the medicine choice came while I was here. It is definitely not a resume padder. It's two years of your life where you are going to be faced with many challenges and you're going to wonder what the heck you got yourself into. I can't imagine what it would be like doing it if I only semi-cared about what I was doing.
In regards to the statement I bolded, can you imagine doing things you don't care about at all? Well, I'm sure this is taking place a whole lot, especially on SDN, definitely more than people are willing to admit. You see applicant after applicant with laundry-lists of ECs. Given that around 22.5% of people ages 16-24 volunteered in 2011 (
http://www.bls.gov/news.release/volun.nr0.htm), I don't think that we can realistically say that the enormous number of premeds (around 80% around matriculation,
unrealistically higher than the national average) are doing things because they actually want to. As you said, you can't imagine what it's like to do things you semi-cared about doing, yet a large number of premeds are doing this and many probably not only don't care, but actually
hate what they do.
So what does this mean for you and the passion you exhibit for Teach for America? Well, the game that premeds play, especially the SDN type, unfortunately downplay the significance of your commitment to Teach for America. I'm not in anyway saying what you did was significant, on the contrary, I think it's great that you are passionate about it, but the large number of premeds doing similar level activities definitely downplays the significant
in the eyes of the ADCOMs. It's always weird when someone on here says that their ECs are actually good because they didn't do them as a checklist item. Well, do you honestly think that anyone would tell an ADCOM that they did an activity as a checklist item? Nope.
I realize that Teach for America is considered to be a considerable commitment in the eyes of normal people. But we're not dealing with normal people,
FOR THE LOVE OF GOD WE ARE DEALING WITH GUNNER PREMEDS! 
I'm sure lots of premeds do activities like Teach for America, Peace Corps, City Corps, long-term mission trips, and just about anything else to improve their application. So you think Teach for America sounds like too much of a commitment for premeds? Not at all, given the competition and difficulty of medical school admissions, people will do anything. What do you think about the people who start non-profit organizations, and sometimes have parents invest $10k+ to make it look legitimate? People here are spending thousands of dollars! So no commitment is too much when it comes to medical school admissions. The ADCOMs have seen it all. I bet there are loads of Teach for America applicants during each cycle, and the ADCOMs will not bat an eye when they see it.
So you're fighting an uphill battle here. I'm sure that you're sincere about this, since you've taken the time to write here. But I'm sure that five other Teach for America premeds who don't give two $h1ts about the underserved will write the same exact things you said. Sadly, this is what the crazy admissions game is. I apologize for the pessimism here. I hope that the ADCOMs are able to see your sincerity.