In Australia, the drinking (and smoking age) is 18. Its probably fair enough. Though most people start drinking before then (I had just turned 15 when i started goin to parties and drinking).

If people are found drinking underage the cops just empty out their drinks and tell you to move on, but if your not causing any trouble they'll usually turn a blind eye.

If you wanna flout the laws, and you look the part, you can often be served at bottleshops, or sneak into pubs before bouncers arrive. Seeing as i had homebrew gear i was also brewing my own alcohol at 17 (I was living away from home as well, not that it mattered, guess who gave the gear hehe - its also available to anyone at most supermarkets).