Westport was a key camping spot for me--it was after the very tough climbing in the vicinity of Legget(going South). However, I don't see how you can close Westport. It was just a hardscrabble strip of land on the ocean with a pit toilet and a drinking fountain surrounded by a swamp. You should still be able to camp there--although you probably won't have a toilet, or water if they shut it off. However, there is a small store to the south of the campground(20-30 minute ride?) where you can resupply.
McGrath is a key one--it is close to LA (in Ventura). But the hiker/biker site in McGrath was a shithole. I hated McGrath.
As for Limekiln, I rode in there and checked it out. It was $35/night, the campsites were right on top of each other, and the scenery wasn't that great. Oregon had some better hiker/biker sites for $5/night. I kept on riding south.
S.P. Taylor is the one that would affect touring cyclists the most. There really isn't another spot to camp between Bodega and SF
There's the hiker/biker site at Mt. Tamalpais(near Mill Valley) but it is off route and up a big climb. I couldn't find the start of the climb, and because it was alread 10pm and all the hotels were booked, I ended up camping in a city park in Mill Valley.
I heard rumors of a hiker/biker site in the Presidio(just south of the GG bridge) that is on the low down.