Yes, you do. ----- This answer contradicts the one found at http://wiki.answers.com/Q/Do_you_need_a_passport_to_travel_within_mexico Reality favors the answer "No, you don't", but much depends on who...
No. You need your passport, and you also need a visa issued by the Mexican government. Such document can be obtained at the Mexican embassy or consulate closest to you:
Embassy of Mexico in...