Travel Documents Required
From Thousand Smiles Wiki
You will need a valid US Passport or other proof of citizenship along with a picture ID in order to return to the United States by land. Please check out the United States Homeland Security web site for more detailed information.
ATTN: Bus Riders
You that you can fill out the Forma Migratoria Multiple (FMM) online and print it out to present at the border so we can save some time. Go to the Mexican Immigration website. Under addresses you can simply write in “San Diego” and “Ensenada”. Under reason for trip, “Other”.
Click below for the website