That kind of 'immersion' would certainly benefit your study of the language. Some universities do offer bilingual studies; meaning that some courses may be in English. Medical and dental schools are that way but the English side is pretty weak. Studying law in Mexico would probably not prepare you to use that education elsewhere. Mexican law is based on Napoleonic Law, not Common Law as in the US and UK, etc. Mexico is only now considering open, verbal trials in a few test areas. Jury trial is not used in Mexico. However, that may be your area of interest if you are interested in studying the various legal systems used in other countries, but that would probably be post-graduate work. I suspect that may also be the reason you don't find Mexico offered as an option for foreign study in law. Now, if you were interested in Medicine or Dentistry, you might find the University of Guadalajara to be an option, as have many medical students from the USA.