Language
Ok, so the principal language in Mexico is Spanish, however it is called Mexican Spanish as some of the words and the dialect is slightly different than Spanish.
Dont fret if you dont speak the language, their English is very good, but they do appreciate it if you try a little.
I bought this Rough Guide to Mexican Spanish, it came in really useful.

MEXICAN NIGHT
FRIENDLY STAFF
Temple of the Owls
In the Pool!