I just came up the Oregon coast from the Ca. Border to Newport. The far southern coast is much more scenic and just breathtakingly beautiful. I would go all the way to Redwood Natl park in Northern Ca on 101.
We found most of the Oregon state parkswe stayed in were open all year or had portions open all year so I dont think fall will be a problem. Oregon State Parks has a great web site...go there and look.
The Oregon state parks are very nice and many have elec and water hookups and some have full hookups and they are very reasonable. We have paid between $22 to $29 with hookups. We particularly enjoyed Humbug Mountain SP, Harris Beach SP in Brookings Or. and Sunset Bay SP near Coos Bay.
I highly recommend them but dont miss the far southern coast it is by far the most beautiful part. Truly dramatic in its scenic splendor.