This all depends on the size of the tacos... if they're tiny like a Taco Bell taco then I think this is definitely a good bet for you at 9-1. Problem is, it's actually more like 4-1 since you have to pay $120 for the tacos if you lose. That makes this a lot closer.
I'm not a big eater, and I'm 100% sure I could eat 25 beef tacos from Taco Bell in 2 hours with absolutely no preparation. I can eat a huge meal and be ready to eat again in 30 minutes, so 2 hours is a really long time. With almost 2 months to prepare you can win this bet if you really try.
I'd want to be making a hell of a lot more than $900 to put myself through that though...
This thread made me really really want some tacos and I can't have one for at least 4 hours.