Updated June 30, 2021
El Chaparral is the southbound border crossing into Tijuana from San Ysidro/San Diego. It's easy to park and get a tourist card in the customs facility. If you got your tourist card online, this is the same office to go to get it officially stamped.
Note: This article only describes the small immigration office where Mexican tourist cards are issued. For resident cards and visas, visit the main immigration office.