Call your local medical group, ask to speak with the travel clinic. They know the latest. However we go to all parts of Mexico and have never had special immunizations prior to going. Ask your doctor for a small prescription for Cipro in case of stomach upset. Also my doctor recommends two Pepto Bismol each morning as a preventive measure. Believe it or not it really does work.
The only negative is your stools will become darker in color. Big Deal!