Documentation: All travelers returning from Mexico now require a passport to reenter the United States. This is a new regulation that has only recently come into effect for people crossing the international border by land. This requirement is very important and bears repeating: All travelers returning from Mexico now require a passport to reenter the United States. Apply for your passport early, since there are lots of applicants right now. You can apply for passports at many post offices and other government offices. A passport costs $85 for children under the age of 16, and $100 for everyone else.
The State department has recently introduced a document called the passport card, which will allow the holder to return to the United States by land or sea when arriving from Mexico, Canada, and some Caribbean locations. It is not valid for travelers arriving in the United States by air or for travelers returning from countries other than Canada, Mexico, or parts of the Caribbean. The passport card is however cheaper than a regular passport; it costs $45 for adults, $35 for children under the age of 16.
Other requirements: The Mexican Government requires that all children under the age of 18 bring a notarized letter signed by all custodial parents or guardians giving them permission to travel in Mexico without their parents/guardians. They must also bring a notarized copy of their birth certificate or custody / adoption degree to establish the parental relationship. The Puentes de Cristo permission form meets the requirements of this letter, but all minors must bring a copy of their birth certificate.
Vehicle Importation: This section only applies to groups traveling by car to the interior of Mexico. If you will be staying in Reynosa, Rio Bravo, or Matamoros, you can ignore this section.
To temporarily import a vehicle beyond the 22km border zone in Mexico you will need to apply for a temporary vehicle importation permit. This process can take as few as fifteen minutes if lines are short, but it is very important to have all your documents in order. You can get your importation permit at many Mexican consulates. If this is practical, it could save time at the border crossing.
Regardless of where you do the paperwork, you will need the following documents:
1) tourist permit of the driver
2) title to the vehicle (preferred) or registration, plus invoice, plus
3) If the driver does not own the vehicle, you will also need a letter authorizing the driver use of the vehicle within Mexico and a copy of the vehicle’s title.
The cost for importing a vehicle is approximately $30 at the border, $35 at a Mexican consular office.