I'm living in Mexico. I went to the U.S. and bought a Nintendo 3DS. Will the 3DS read the game if I buy the game in Mexico?
Mexico games share the same region code as the U.S. (NTSC-U) and therefore do function properly in devices from the U.S.
Note that these countries sometimes have games made exclusively for them, usually in French (NTSC-C) and Spanish (NTSC-M) respectively, these games however will still work in the other countries of this region without any modifications or lockout disabling devices.