Well I'd probably ask over on the CA Gardening forum to get the best advice from locals. But Googling
'fall garden planting dates southern CA' pulls up lots of info too.

One gardening article from the LA TImes talks about the effect of La Nina (if it develops again this year) and suggests Sept. planting. If it doesn't, then you can plant earlier apparently.

If you can determine what your average date for the night temps to drop down out of the 50s then you can use the DTM of your varieties to count backward to planting time and back up 2 weeks more.

But I'd sure check with the CA Gardening forum. Surely it is a topic that gets discussed there.

Dave