I think that the policed issue is more related to WHERE than WHAT. It seems seen as unfit for minors (under 18) to hang around in bars, some Car Washes and similar nite clubs and establishments. On the other hand, one can quite often see kids been granted the privilege of taking a little more than just a sip out of a big Presidente bottle... after all it is called "una familial" and without kids, there is no family.
But I seem to observe less youths hanging around stone drunk on the streets on Saturday nites than in most other countries which have stricter rules.
Actually, in general, while quite a lot is being guzzled here... I seem to see less alcohol excess'
on the street than lets say in some Andean countries and even some EU countries. Fiestas end earlier and with less damage too, in general.
... J-D.