I've been to Mexico (Mexico City, Guadalajara and Chihuahua) many times before, and have never had any difficulties in getting into the country; even doing some development work for a short time over there. However, two months back, I had my first time being driven into Mexico, via Tijuana. I had not anticipated any difficulties, after asking our local rep firm the week before "Will there be any problems?".
The first hint of trouble was when we could not find anywhere to park, to go through the documentation procedures. "They've gotten rid of all the parking spaces!" said Rick (the driver), so we parked in a zone where it was clearly marked "Do not park here", and Rick coughed up $10 to a shifty-looking guy who held a sign saying "I will watch your car and make sure nothing happens to it". The art of the grift: and we were just 100feet into Mexico! Then we found out (with Mexican immigration's poor English and my awful Spanish) that I needed a "Letter of Invitation" from the company I was visiting. We finally got one faxed through and 2 hours later were on our way. During my time in the office I noticed that all the notices were in Spanish, except for the one taped to the table saying "Non-US citizens must have a letter of introduction", but since you would have to come here to read that it was hardly a pair pre-warning.
Anyway, $23 each got of us a short-term visa and on we went into Tijuana: which was as poor and run-down as anywhere I've been in Mexico. The cops were going round in pairs, since the recent arrest of a druglord had angered the local cartels so much they had started shooting up police stations. Godspeed to all those non-corrupt, hardworking Mexican cops.
Lunch with the customer was interesting: Mexican version of Chinese food (wantons like dried vermicelli). I had to warn one of my companions, as she was about to put ice in her glass and fill it with soda. "Just drink it out of the bottle". A lot of people make the same mistake - avoiding the tapwater like crazy, but forgetting what goes into the ice, and what is used to wash the glasses.
Later that day, we drove back fine into the US: slow but no real hold-ups. I also noticed for the first time all the carefully-bilingual signs and notifications on the way back, paid for care of the US taxpayer.
Safe travels! Des