Use the lemons served in restaurants, as the juice has antibacterial properties. It's possible you may eat or drink something that isn't quite right while on vacation. If you experience diarrhea, there are several ways to treat it. Avoid anything that will further irritate your stomach such as alcohol, sodas or coffee, and drink plenty of purified water to replace lost fluids. Pepto bismol is a time proven relief for diarrhea.
Most pharmacists can recommend the proper medicines, which are inexpensive and effective.
You don't need a prescription in Mexico for many drugs and a trip to the pharmacy will usually suffice for most traveller's complaints. There are many good doctors in Puerto Vallarta. Dr. Arturo Flores, tel. 224-7876, or Dr. Maria Guadalupe Lewgot, tel. Weather Puerto Vallarta enjoys well over 320 days of sunshine per year and has basically two seasons.