Took the Blue Line trolley all the way down to the border and walked around Tijuana for a few hours. It's a peculiar thing to walk over a national border - there's a little marker, but that's it. And there's no border control or customs check entering Mexico.
If you stayed right around the crossing, you might think that one out of five Mexican men play guitar. Apparently playing in the cafes right there is a booming business. And every store you walk by, there's a guy trying to get you to come in, hawking his wares. Silver bracelets. "Cuban" cigar (almost certainly not Cuban.) Ponchos - I guess at least these would be real ponchos and not Sears ponchos. The usual tourist crap t-shirts.
Tremendous number of dentists and pharmacies right over the border, catering to Americans who can't afford health care at home.
Walked the whole length of the Avenue de Revolucion, past where the tourist zone peters out. Down past the "Tijuana Swap Meet", where booths made out of hung tarps sell clothes and DVDs...like a ghetto third-world shotengai; down to a few blocks of car repair joints, where the cement is all cracked up.