You *must* have reservations. I recommend that you read the RV topic in the Top Questions on the right side of this page (full TA website.) One of the articles is about Where To Stay.
Also read about the Hwy 1 closure.
I 100% agree. Now through early fall is busy busy camping/RVing time. Many Campgrounds are full and have been for months. You'll probably have more luck with RV Parks.
For SF-- there isn't a great option... KOA in Petaluma does day tour to SF...
Pismo has a really nice RV Park. But check Pismo, Morro Bay and San Simeon SP