Waves or Flat water? .. The seabreeze in summer is SW which is perfect for most of the WA coast. There are a couple of points in Perth which generate waves but usually small. If you're coming for a short visit, then head north or south for the best conditions - see
windsurfwa.com/index.html which has all the info you need on travelling, and spots up & down the coast...
windsurfwa.com/index.html/WA/spots.html gives text details on many metro spots...
Enjoy .. Laurie