Esperanza recommends that all participants have a passport or passport card.
This will reduce the chance for slow downs or delays when re-entering the United States.

From the United States Department of State website (updated February, 2011):

ENTRY/EXIT REQUIREMENTS

For the latest entry requirements, visit the Embassy of Mexico’s website or contact the Embassy of Mexico at 1911 Pennsylvania Avenue NW, Washington, DC 20006, telephone (202) 736-1600, or any Mexican consulate in the United States for the most current information.

Since March 1, 2010, all U.S. citizens – including children – have been required to present a valid passport or passport card for travel beyond the “border zone” into the interior of Mexico.  The “border zone” is generally defined as an area within 20 to 30 kilometers of the border with the U.S., depending on the location. Regardless of the destination in Mexico, however, all U.S. citizens age 16 or older must present a valid U.S. passport or passport card to re-enter the U.S., even by land.

All Americans traveling outside of the United States by air, land or sea (except closed-loop cruises) are required to present a Western Hemisphere Travel Initiative (WHTI) compliant document such as a passport or a passport card. While passport cards and enhanced driver’s licenses are sufficient for re-entry into the United States by land or sea, they may not be accepted by the particular country you plan to visit; please be sure to check with your cruise line and countries of destination for any foreign entry requirements. U.S. legal permanent residents in possession of their I-551 Permanent Resident card may board flights to the United States from Mexico.

The U.S. passport card has been in full production since July 2008. Beginning March 1, 2010, Mexican Immigration began to accept the passport card for entry into Mexico by air; however, the card may not be used to board international flights in the U.S. or to return to the U.S. from abroad by air.   The card is available only to U.S. citizens. Further information on the Passport Card can be found on our website. We strongly encourage all American citizen travelers to apply for a U.S. passport well in advance of anticipated travel. American citizens can visit Bureau of Consular Affairs website or call 1-877-4USA-PPT (1-877-487-2778) for information on how to apply for their passports .

As of May 1, 2010, non-U.S. citizens with valid U.S. visas may enter Mexico with the U.S. visa, and do not have to obtain a Mexican visa.

Minors

Mexican law requires that any non-Mexican citizen under the age of 18 departing Mexico must carry notarized written permission from any parent or guardian not traveling with the child to or from Mexico. This permission must include the name of the parent, the name of the child, the name of anyone traveling with the child, and the notarized signature(s) of the absent parent(s). The State Department recommends that the permission should include travel dates, destinations, airlines and a brief summary of the circumstances surrounding the travel. The child must be carrying the original letter – not a facsimile or scanned copy – as well as proof of the parent/child relationship (usually a birth certificate or court document) – and an original custody decree, if applicable. Travelers should contact the Mexican Embassy or the nearest Mexican consulate for current information.

Tourist Travel

U.S. citizens do not require a visa or a tourist card for tourist stays of 72 hours or less within the “border zone”. U.S. citizens traveling as tourists beyond the “border zone”, or entering Mexico by air, must pay a fee to obtain a tourist card, also known as an FMM, available from Mexican consulates, Mexican border crossing points, Mexican tourism offices, airports within the border zone and most airlines serving Mexico. The fee for the tourist card is generally included in the price of a plane ticket for travelers arriving by air. U.S. citizens fill out the FMM form; Mexican immigration retains the large portion and the traveler is given the small right-hand portion. This FMM is normally white, blue and green in color. It is extremely important to keep this form in a safe location. Upon exiting the country at a Mexican Immigration (INM) departure check point, U.S. citizens are required to turn in this form.   We are aware of cases where U.S. citizens without their FMM have been required to change their flight (at personal expense), file a police report with local authorities regarding the missing document, and visit an INM office to pay a fine and obtain a valid exit visa. In other cases, travelers have been able to continue their journey after paying a fine. For more information visit the INM website .

Mexican Law

While traveling in Mexico, American citizens are subject to Mexican law.  An arrest or accident in Mexico can result in a difficult legal or medical situation, sometimes at a great expense to the traveler.  Mexican law can impose harsh penalties for violations that would be considered minor in the United States, and U.S. citizenship in no way exempts one from full prosecution under the Mexican criminal justice system.  If U.S. citizens find themselves in legal trouble, they should contact the closest U.S. Consulate, U.S. Consular Agency, or the U.S. Embassy in Mexico City. (see “ Contact Information ” below).  U.S. consular officials in Mexico can visit detained American citizens in prison, provide information about the Mexican legal system, and furnish a list of Mexican attorneys, among other assistance.  U.S. Consular officials cannot arrange for Mexican officials to release detained American citizens.

Driving in Mexico

American citizens planning on driving to Mexico should carry a valid driver’s license at all times.  U.S. driver’s licenses are valid in Mexico.  Mexican law requires that vehicles be driven only by their owners, or that the owner be inside the vehicle.  If not, the car may be seized by Mexican customs and will not be returned under any circumstances.  We strongly recommend that you purchase a full coverage insurance policy that will cover the cost of bail.  Please be aware that if you are involved in an automobile accident, you will be taken into police custody until it is determined who is at fault and whether you have the ability to pay any penalty.

Consulate General in Tijuana: Tapachula 96, telephone (52)(664) 622-7400. During non-work hours, an American official may be reached at: 011-619-692-2154 (from Mexico) or 619-692-2154 (from the U.S.).