No worries. Carry your own water in or drink bottled water provided. Montezuma's revenge is not lurking around every corner. Get your teeth cleaned and eat at one of several local eateries. Been doing it for years. Haven't died or caught anything I know of yet. Just use good sense. It is a great cultural experience to go there. Never felt threatened. If you are on prescription drugs, check at the "purple pharmacy". Either have a photograph of your overpriced American packaging or a copy of you prescription. You will pay 50% or less than what you are being ripped off for in the US.