You can enter Mexico without a visa showing your passport and the "migration Form for Tourists, Transmigrants, Visiting Businesspersons, or Visiting Consultants", which you can obtain from travel agencies, airlines, or at your point of entry into Mexico. This option also applies for permanent legal residents in the USA, Canada or Japan, regardless of nationality.

For more information, please refer to http://www.inm.gob.mx/EN/index.php