Parece que você deve ter um passaporte válido para entrar no México. os seguintes links:
Consulado do México em São Francisco, link
Effective March 1st 2010, all US Citizens are required to present U. S. Passport or U.S. Passport Card when entering Mexico (traveling by air, land or sea).
US Permanent Residents traveling by air, land or sea to Mexico are required to present a valid Permanent Resident Card. Plus a valid and not expired passport or travel document. If you do not have that card consult other documentation also accepted to prove the US Permanent Residence status.
Consulado do México em Detroit, link
US Permanent Residents traveling by air, land or sea to Mexico are required to present a valid Permanent Residency Card, as well as a valid passport from their country of origin or travel document.
Consulado do México em Anchorage link
All permanent residents of the United States who are holders of a “Permanent Resident Card”, also known as “green card”, who want to travel to Mexico as tourists just need to present their passport and “Green Card”.
Mais importante, o Timatic (o banco de dados que as companhias aéreas usam) diz que
Passport required.
- Passports and/or passport replacing documents must be valid on arrival.
- Warning: if departing from the USA (regardless of any destination passport exemptions), a valid passport and/oraccepted departure document For details, click here is required by the US immigration authorities.
Passport Exemptions:
- Holders of emergency or temporary passports.
Os funcionários da companhia aérea usarão essas informações da Timatic quando decidirem permitir que você embarque em seu voo para o México. Provavelmente, eles não deixarão você embarcar no avião (mesmo que um oficial de imigração no México possa deixá-lo entrar).
Eu sugeriria que você contatasse um consulado mexicano e sua companhia aérea, e verifique com eles se você precisa de um passaporte válido.