Rainbow Air in LGB seem ok about renting us an aircraft to do the Baja trip when we enquired but required we do the trip once with one of their instructors - they literally referred to it as the Baja checkout. I think a lot of it was to do with customs procedures rather than making sure you could actually find the place, guess they dont want their aircraft filled with bullet holes!
Did hear a story of one guy who managed to land at Tuijana airport rather than Brown Municiple and found himself with an armed reception commitee.