It depends on the quality of your local water source. Places like Texas(my grandparents have a vacation house down there, so I've had the graces of runny bowels a great many times on my visits) have terribly unclean water. I'd say the same for mexico, too. I live in Minnesota, and the water is great up here. If I were you, I'd do a quick google search of the water quality in your area. If it has a terrible reputation, go with bottled water or something of the sort.