Well the bar in question is in Boca, which I guess is quite technically a college town (PBCC, Lynn University, and FAU are all within the city limits), but underage drinking here works the same as pretty much everywhere. Gas stations and places of those nature don't really care, and will generally just charge you more if you don't have an ID. Most bars/clubs with a bouncer won't let you in, but if you do get in with an under-21 band or something, the bartenders won't generally notice if you go to the bathroom and rip it off.
This bar is really cool. Since everyone who works there (only 2, maybe three people tops, and only one or two at a time) is British, they really don't give a flying fuck how old you are.
Gainesville (where UF is, where I go to school) is easier to drink in, if only because there are so many more bars and clubs to choose from (not to mention parties), and most of them will let you in at 18 with a brightly colored wristband, and then serve you if you rip it off.