One of the stigmas that used to be associated with traveling to certain parts of Mexico was that it was not safe to drink the water. Although there was no certainty that one would get sick after drinking the local water in Mexico, the likleyhood of developing intestinal trouble did increase for those who did. Fortunately, those days are fading fast.
There are still parts of Mexico where drinking the water from the tap can be a risky proposition. Certain parts of southern and inland Mexico such as Chiapas have not yet taken the necessary steps to purify the local water, and some travelers may still get sick with moderate exposure to local waters.
For years word has passed from traveler to traveler that there are several ways to mitigate the likleyhood of getting sick when traveling in Mexico. Not brushing your teeth with the local tap water, not drinking drinks or cocktails with unpurified ice cubes, and not eating fresh fruit or vegetables that have been washed with the local waters were three good ideas that made sense.
But being on the defensive while traveling in Mexico was too much like work for most tourists, not enough like being on vacation, and there were still some people getting sick even though they made efforts to avoid contact with the local water. A more definitive approach was necessary.
A good example of a Mexican destination that has made exceptional efforts to provide safe water is the state of Jalisco. The primary tourist town in Jalisco, Puerto Vallarta, had a significant water quality issue in the mid to late 1970's. Understanding that this issue would stifle tourist growth in the area, the Mexican government spent millions of dollars developing a safe water purification system for the area. This state of the art system has greatly reduced water-induced illnesses for travelers visiting Puerto Vallarta.
DRINKING THE WATER IN BAJA
Carlos Fiesta says "When you aren't sure about the water...drink a beer."
The Baja Peninsula has never had the significant water quality problems that mainland Mexico had. Yes, there were some cases of intestinal problems (touristas) for travelers who visited some parts of Baja, but for the most part Baja waters have never been a huge problem. In general, the further south in Baja that one traveled the less of a problem the water was.
Drinking water in the northern parts of Baja such as Tijuana and Ensenada today come from local underground aquifers and from local reservoirs. These sources of water are subject to various types of contamination, which are usually removed from the water before it reaches the local population and the tourists.
In the southern parts of Baja much of the water comes from the tall mountains that run along Baja's spine, water that seeps into underground aquifers before being piped to the local towns. This fresh rain water has very little opportunity to become tainted before it reaches the local populations, so illnesses are even more infrequent.
Sitting at the bottom of the Baja Peninsula, water in Los Cabos is some of the best in Baja. The local waters start thousands of feet above Los Cabos in the very tall mountains north of Cabo, drain down into local aquifers, and then are treated locally and then often treated again at the hotel or restaurant level. Tourism is just too important to let bad water become a factor.
Despite all of the precautions made to keep the water supply safe, there are still isloated cases of travelers getting sick in Baja. While some of these illnesses may be atributed to the local waters, a significant part of these cases are caused by tourists pushing the body too far while trying to maximize valuable vacation time. Drinking too much, staying up too late and running on minimal sleep, and getting too much sun can all contribute to wearing down the body's defenses and setting the stage for the local bacteria to enter the body and raise hell.
Staying healthy in Baja is possible, and even probable, for most visitors. Getting enough sleep, drinking in moderations, avoiding super-spicy foods, checking to make sure the water and ice you are consuming is purified, and generally being aware are steps that all visitors can take to minimize risk.
Those that do catch a bug usually find that it lasts a day or two, and they are back in the vacation mode with very little delay. Lomotil and Pepto Bismol usually work wonders to firm up the soft spots in a short period of time.