Hmm, interesting concept - go to third-world countries and see if you get diarrhea. That doesn’t sound fun, and it reminds be of a horrible incident in Egypt a few years back.
On the plus side, you do get a free trip, and if the medication you’re given works, then you win. What’s better than a trip to Mexico? A free trip to Mexico, that’ s what. Just in case, though, I would pack some Imodium.