Van Badham, a prolific and very smart playwright with whom I am fortunate to be acquainted, has a play currently on at the Old Fitzroy Theatre. It's called Poster Girl, and it's very funny and very well-acted. (But don't just take my word for it: here's a review from aussietheatre.com, and here's another from stagenoise.com.)
It's still got a week and a half to run, so go here to buy tickets! I heartily recommend buying the "Beer, Laksa, and Show" package, because the laksa is quite nice, and if you decide you don't like the plain old beers that are available as part of the deal, you can pay another $1.60 (or so) at the bar and upgrade to a nicer one. I can't think of any reason not to spend an evening doing this, unless you live way far away from Sydney.