Border Tourist Assistance As of March 2010, all citizens of the United States must present a valid passport when entering Mexican territory by any means of transportation. There are no exceptions for minors. Stays less than 72 hours within the border area, do not require a visa or tourist card.
When crossing the border area or entering the country by air, US citizens must pay a fee to obtain a tourist card (FM-T), which is available at border crossing points, Mexican tourist offices and Airports located within the border area. Major airlines provide the tourist card (FM-T) during the trip.
The information that has to include the form is: number of days to be spent in the country, passport number, destination, city of origin, among other data. Business travelers must complete and submit the FM-N 30 Days form, which will allow them to do business, but not accept a job for a period of 30 days. Those who need to enter the country for reasons other than tourism and business, or to stay for more than 180 days, will need to obtain a visa and must carry a valid passport.
US citizens contemplating working or living in Mexico must apply for the Mexican visa at the Mexican Embassy, located at 1911 Pennsylvania Avenue N.W., Washington, D.C. 20006; Telephone (202) 736-1000, or at any consulate of Mexico in the United States.
All US citizens 16 years of age or older must present a passport in a book or card to re-enter their country by land or sea. Children under 16 years of age may re-enter the United States via land with a legal document (naturalization certificate or birth certificate). When entering the United States by air, all citizens, irrespective of their age, must present a passport in a United States book. The passport in card is not valid to enter the United States by air.
Foreigners originating from countries with which the Government of Mexico has signed visa suppression agreements will not be required for a visa. Here you will find the list of countries that need a visa to travel to Mexico.