COMPLETELY CORRECT ANSWER as of July 2011: After reading about two dozen forums I was terrified to cross while on vacation. Here is my experience. A passport is required/desired, but Tijuana 1) does not check you going in (unless you look suspicious) 2) When leaving they have two distinct lines setup . . . One for those with WHT documents and another line for those without. The line for those without equates to those traveling with only basic documents i.e. (State issued drivers license and a birth certificate. When I came back across it was the easiest time I have ever had. My documents were looked at, I was asked maybe 2 questions and nothing was searched . . nothing at all . . . it was simple. BTW: I walked across, I would never driver across for many reasons.