Agra. May I suggest you post on SA section. I think it can get pretty good there and waves also but I don't know much about their seasons. If you google 'windsurfing in WA' you will probably find a few travel logs from windsurfers from the east caost and you can plan your destinations.
WA can get a run of a few days only 10-15 knots but then you have time to do all the touristy stuff. Once you leave Perth the state is empty and driving around is easy especially compared to Syd & Bris.
I considered moving there (WA) but I think my wife realised how reliably windy it gets for half the year and idea get veto'd for about 5 years