San Ysidro is still the busiest border crossing in the world. It's nominally 'closed', but still open for trade. In normal times you don't need a full passport,

San Ysidro is still the busiest border crossing in the world. It's nominally 'closed', but still open for trade. In normal times you don't need a full passport, either- just a passport card is fine, and realistically a CA driver's license will get you through without trouble. It kind of has to be that way- Tijuana and San Diego are far too closely tied together for much else.