Be sure and drink bottled water not tap water. The resorts always, at least in Mazatlan, wash the vegs etc in purified water.
Many people that get sick in Mexico are sick from drinking too many margaritas and not enough water. They get dehydrated and that will give you the same symptoms at the Montazumas revenge thing. Have fun and enjoy the local food and drink, just be sure to drink some water, or gatorade, or better yet pedialite. Do it for your body and for your vacation.