He didnt ask if its legal to be drunk in public, he asked if you can drink on the streets.
Depends where you are really, if you are in Surfers then technically you arent supposed to, but cops dont enforce it unless you are right near clubs and stuff i.e right on cavil avenue or on the beach. When i was there i always took a drink with me for the walk to the clubs, massive police presence and i never even got spoken to about it, saw heaps of people doing the same aswell.
Of course they might crack down on it this year so better safe than sorry, put your drink into a container that looks non alcoholic e.g empty coke can or maccas drink cup.
What some of my friends did was buy a slurpie, drink some and then add alot of vodka to it. Totally legit looking and a tasty way to get smashed on the sly.