I have neven been caught.
I have been stopped by the police many times, for example:
A while ago I was with some friends just, around the city, and a police stopped us just because they felt like it and my friend didn't had a license,so the officer asked us for money(as it usually happens in Mexico).
And that was it... he let us go...
And getting caught for drinking is not impressive,
Here is very common seeing a 13 year old kid drinking, and the legal age to buy beer is 18, but if you look older, or you know the guy at the store, that's all you need.
I've never been a witness in a crime or something like that.
But I have seen people get shot with AK-47's, but here, being a witness is the same as comitting suicide, because a drug lord, a cop, and a politician are the same thing here.