The U.S. Customs & Border Protection website lists the identification documents necessary for re-entry back into the U.S. at:
As of June 1, 2009, the requirements are:
A) A U.S. passport book, or
B) A U.S. Passport Card
If you are driving yourself into Mexico we recommend you travel via the TECATE border crossing. An alternate border crossing would be the OTAY MESA border crossing.San Diego to Tecate Border Crossing (5am-11pm)
San Diego to Otay Mesa Border Crossing (24 Hrs.)
A real-time listing of wait times at the San Ysidro, Otay Mesa and Tecate border crossings. This nifty web application will also work on any internet enabled PDA or phone that has service in Mexico.
Click on this link, or point your browser to: Rancho La Paloma