Mexican law enforcement (like many other things in Mexico) will almost always be shades of grey as opposed to black and white. I have had a gun drawn on me for "illegal parking" in a very similar incident as described by Roberto. And that guy didn't want to go to the Comandancia, he wanted cash on the spot, and what the hell are you supposed to do in the moment?
For most minor infractions like stop signs or speeding I totally agree that its better to ask for the ticket- BUT, for anything alcohol related it is a dangerous game even if you think you are in the right. Let's forget the case where you would clearly be guilty, i.e. 15 beers at Wrecked and then crash into a sand dune. I think the main point of Joe's post is to ask whether you can have 2 or 3 Dos Equis with dinner at the Malecon and drive home with no worries.
For this case I will draw on personal experience. About 10 years ago in Nogales, I crossed into Mexico to play pool with a buddy who is a Mexican national. Over the course of 3-4 hours I had about a beer an hour- I'm 6'5" so for me that's almost like lemonade. On the way home we got pulled over for no reason ("revision de rutina") and I told them the complete truth, i.e. I've had a few beers but *clearly* not drunk.
"OK, señor, we'll have to go to the comandancia to see the "Doctor". My friend was immediately nervous and told me to give them 500 pesos. I was defiant and knew I was in the right, and wanted no part of a bribe- I thought I'd be cleared with a breathalyzer. To make a long story short, after more than a hour, the "Doc" gave me a breathalyzer and it was 0.03- "OK, so I am free to go, right?" "Sorry, amigo, maybe in your country yes, but in Mexico we have a different limit." "OK, what is the limit?" "ZERO, señor."
"Wait, I ADMITTED that I had 3-4 beers, why did we have to go through this whole charade then?!" "Sorry amigo, welcome to Mexico." I was in jail 3-4 hours in a disgusting cell that even Hollywood would have a hard time imagining. I had to pay 2,000 pesos to the "Judge" (who put the money directly into his wallet), and another 2,000 to get my car back. After that experience, I will almost never drive at night even after 1 beer- during the day I usually don't worry as much since the worst rats usually like to hunt after dark.
The underlying message of not paying bribes is *generally* correct. BUT, it is also somewhat eye-rolling to hear "just take a taxi everywhere you go all the time if you've had 1 beer" passed off as a completely normal state of affairs. That is NOT a "normal" situation, and it is important to be clear why- you are not in your home country, and in the worst circumstances in Mexico, the police can and do make up the rules as they go along. This may not be what everyone wants to hear, but its the truth, and better to acknowledge it and adjust accordingly.
Anyway, I love Mexico dearly, and as a friend once told me about being in the grey area: "You gotta take the good with the bad."
