Leighton beach - Great for SW (main wind in perth summer) - Huge beach for landing and launching and not many swimmers as they all tend to go down to cottesloe beach - No issues with security.
You can do a long downwinder from leighton beach to trigg beach or city beach that takes roughly 2-3 hours
Another popular spot is Melville water. This is good for beginners as the water doesnt get deep until you are about 100m off shore however on windy days it is absolutley packed and the beach is not built for setting up kiting gear. The good thing is that there is heaps of people to help you launch and land. Watch out for the pure noobs learning down the beach.
Woodmans point is apparently and excellent location however I've never been there
Pelican point is a second river location in perth metro. However i would advise against not going here as you do not get blown downwind into water, you get blown into trees. There is a small peninsula that runs perpendicular to the wind which can in most situations be very dangerous.
Point Walter is a great location for an easterly wind. It's basically a sand spit that runs out on the river about 300m. If you have balls of steal you can attempt to jump the spit
