Mexico uses the metric system, so distances are in kilometers, weights are in kilograms, gasoline is sold by the liter, and temperatures are given in Celsius.
Chiapas [1] is in U.S. Central Standard Time. Daylight Savings Time is observed April–October, though be aware that the hour switches on different days in Mexico and the United States.
Mexico uses the 60-cycle, 110-volt AC current common in the United States. Bring a surge protector if you plan to plug in a laptop.
Links:
[1] http://www.moon.com/destinations/chiapas