Saw this water filter that is good for viruses and bugs that doesn't use chemicals. You could use it in Mexico to drink the water safely. Cheap at between 150 to 400 bucks. Just thought you guys might want to know as it is a great way to stop a trip to the doc and save you from an emergencies.
http://www.ted. com/talks/ michael_pritchar d_invents_ a_water_filter. html