Yep, Salmon Bay is the safest option, you can even get the Bayseeker bus out there with your gear if you don't feel like riding. Bickley Bay (flat water) down near Kingston Barracks is another option closer to town, you can practice you start for the L2L, coz thats where they leave from, but i wouldn't head to far out. There is other spots if you are chasing waves.......pretty much stick to the South side and there is no moorings to get in your way (except for Porpoise Bay) and you end up back on 'The Rock' if it all goes pear shaped (in a SW that is).
Oh and you are not allowed to kite the salt lakes.
I've kited Bickley Bay a lot and Salmon Bay a bit. Bickley Bay is pretty easy to get to but it's flat water and gusty on a seabreeze. Not too bad. And if you go out too far and get into trouble, you ain't gonna get onto the island without a rescuer. So if I'm by myself I just stay where I'll get blown back to Rotto anyway. Make sure that if you set up on the point that you aren't walking on fairy tern nests (probably this time of year and definitely in summer) or people will get real upset. And they are damned hard to see. If you see lots of small terns fishing there, then there's probably nests on the ground there. They aren't there every year.
Salmon Bay is a bit of fun and quite practical to ride there. Tricky to launch and land though. It's only about a 15-20 minute ride, and not as hard as you'd think. I've been starting from about where the bus stops and walk west along the beach a bit.
Bickley Bay should be good in a southeaster, I just haven't done it.
I saw a guy sailboard to Rotto from about south beach or somewhere, he said. In the seabreeze. He got withing about 50m of natural jetty and couldn't do the last bit because he kept running out of wind as he got near the beach. I had to get him with a ducky. So if you come from the mainland, you'd probably need to aim to come in at Bickley Bay or Salmon Bay, so you could come in with the wind.
If anyone does the downwinder from Rotto to Pinnaroo, I'd be keen. I guess it could be done.
I checked. You aren't allowed to either kite to or from Rotto, whether it's Hillarys or Freo or south of Freo. The Lighthouse to Leighton event is allowed of course.