A passport is hands-down the best form of identification and proof of citizenship. I recommend that you get a passport for travel to Mexico, and if you'll be entering the country by air, it's necessary. If for some reason you are unable or you do not want to get a passport, for travel to Mexico by land or sea the following documents are acceptable travel documents for US citizens:
- Passport card
Issued by the U.S. Department of State, this passport substitute is credit-card sized and valid for entry into Mexico by land or sea. The passport card is not accepted for air travel. Read more about passport cards, and find out how to apply for one.
- Enhanced Drivers License
Enhanced Drivers Licenses are proof of citizenship and identity. These special drivers licenses are valid for travel to Mexico by land or sea, but are not valid for air travel. Only available in some states (Michigan, New York, Vermont, and Washington). See individual state licensing departments for more info.
- SENTRI Card
The SENTRI Card is issued by the U.S. Customs and Border Protection to pre-approved travelers who cross the U.S./Mexico border frequently. It has the added benefit of access to dedicated commuter lanes for crossing the border. The card is valid for 5 years.
- FAST card
The FAST card provides expedited travel to pre-approved commercial truck drivers between the U.S. and Canada, and U.S. and Mexico borders through dedicated lanes.
For permanent residents of the United States, the I-551 Permanent Resident card is required for return to the U.S. For entry into Mexico, you will need to present a passport.
As of March 1, 2010, a passport is required for Canadian citizens traveling to Mexico.
Citizens of other countries:
Passport, and in some cases, a visa as well.