No mexican I know drinks from the tap or a river. They drink bottled water just like any of us. I think there is one place in Guerrero and some places in Cuernavaca where residents can drink water out of the tap. Bags of ice from E-pura or bonafont or crystal, is always made from purified water.
We use 5 gallon jugs of purified water at home for everything. Yes we have different bugs in our stomachs now, baja does too if he eats tacos de carne asada on the side of the highway. We have to de-paracite once or twice a year and we have to disinfect all fruits and vegetables.