I am down in ravensthorpe atm which is about 150km west of esperance. From what I can tell, for the most part if its extremely hot in Perth then theres a good chance for some decent wind. Having said that, for the past week, it has been pissing down with rain, about 20 degrees and I have been wearing winter gear for half the day!!
Today is meant to go off though.
As for best time...apparently now till february is the best.
The beaches down here are the best I have ever seen! Absolutely unbelieveable.