What documents or requirements are needed to visit Mexico?
Many countries including the US, Canada, the European Union do not need a Mexican Visa to visit Mexico for up to 180 days.
Your passport is required and must be valid (not expired) at the time of entry into Mexico. Your passport should be valid for a minimum period of six months. (If you are staying for a short vacation the immigration agent will determine if you can stay even though your passport might expire in less than 6 months.)
US Citizens do not need visas for tourism. They are granted an 180-day visitor permit upon arrival in Mexico. If you are staying for more than 180 days you do need a visa. You will be required to fill an FMM or Forma Migratoria Multiple. These forms are made available at the airport, check points or provided by the airline.
You may be required to show your airline tickets, hotel reservations or travel itinerary by immigration officers.
Passengers who are transiting in Mexico, through an international airport, can do so without a visa if their connection time does not exceed 24 hours.
All visitors entering by land and traveling farther than 12 miles into Mexico or staying longer than 72 hours must obtain a Forma Migratoria Multiple to present at checkpoints within the country. Foreigners, who enter the country by land, can obtain it through the facilities for the international transit of persons.
There is a list of countries in addition to the US, that do not require a Visa to travel to Mexico can be found here.