Look, if you’re going at the end of july, I would go to the doctors’ asap because some of the shots you get have to be taken 6-8 weeks before you go for them to take proper effect. (www.cdc.gov lets you know all the vaccines you need)
A tip on the bottled water—a few times while I was there, I got a bottle that had just been filled up from the tap and then sold again, so make sure you check that the seal isn’t broken before purchasing it.
I didn’t get sick at all except one time when I had fish inland (not near the coast). They figured it was because there aren’t refigerated trucks or even refigerators most places, so it was probably bad. So no fish inland and you’ll be great. It’s a beautiful country with amazing people. Have a great time!