LOL when I saw this thread I had to respond!! I've had Montezuma's Revenge TWICE while traveling to developing countries (i.e., Peru and the Philippines). Trust me, once you've had it, you will do anything possible to not get it again!
My best advice is to visit the Center of Disease Control website. They have good tips on what to avoid eating when traveling to developing countries. My own top two recommendations are:
1). avoid eating food from street vendors. I'm a pretty adventurous eater, but I did this once and got laid out for 3 days.
2). avoid eating fruits/vegetables that you are not sure were washed with filtered water. The only time I will eat fruits/vegetables in a developing country are when I wash the food myself.
When my FI and I went to Peru last year, we got prescriptions for "traveler's diarrhea" (ciprofloxacin HCl--i think it's the cipro everyone else on this forum is talking about) I didn't use it (I'm a believer of just letting this pass their course) because I got sick at the end of my trip, but I wouldn't think twice about using it if it interfered with my wedding day!!!!