Rule ot thumb for Mexico or travel in general! For Mexico resort, all is good, water and food. In town, still no problem as long as it is in a good spot. Bottled water, well if buy from a vendor, wipe off the bottle around the lid, for it may of been in ice water that is not safe for us. For the most part, PV is very very modern, most speak English and it is easy to get around the town and it has always been a safe place for me to wonder around in by myself, just have to be aware and confident.
The big thing is to stay with what you usually eat, watch out for the black beans, they are a bit more potent then the American kind, lol.
Another note, when one flies, upon landing, take a lot of Acidulous to restore the natural bacteria that is destroyed upon flying. It will make all the difference in the world.
I am sure there are other things, but it is getting late, so if you have a Q., let me know will find out for you!