Hi, I've just got back from pretty much the same trip a couple of weeks ago, so here's some fresh info on where we stayed en route. We started at Tillamook so I can't help with anything further up.
RV park, Pacific City - meh, nice and close to the beach and some bunnies hopping around but not the most scenic environment.
Beachside SP (H/B) - quite nice, no other campers in h/b other than a colourful character from Kentucky pitching up very late on his motorcycle!
Sunset Bay (H/B) - scenic, popular h/b section so very sociable.
Gold Beach - rest day, so we stayed in a motel for a couple of nights. Unremarkable but nice to sleep in a real bed.
Mill Creek (H/B) - lovely site amongst the redwoods, but you need to descend a 2 mile long hill off Hwy 101 to get there which is steep in places, which means you need to climb up it again in the morning. Hard work!
Patrick's Point (H/B) - another deserted site, potentially very scenic (but very foggy when we were there) and good access to rugged coast paths
Burlington (H/B) - possibly our favourite site, amongst the huge redwoods part way along the Avenue of the Giants. If I was doing the route again I would consider stopping here (or Standish-Hickey) to fit in some hiking.
Standish-Hickey - see above. Also, there's a quirky but nice store on the road opposite which is a convenience store and restaurant/bar. Swimming also available in Eel River. A good stop before tackling the climb after Leggett.
MacKerricher Beach (H/B) - Great location next to the beach with excellent wildlife opportunities. We spotted whales! (Just about!)
Salt Point (H/B) - Nice forest environment but one of the more disappointing sites, particularly in that it was the only h/b site that didn't have showers, plus the warden was about the only one we didn't find to be particularly friendly.
Samuel P Taylor (H/B) - As an update to above, the showers are working fine! :-) Another nice site, following Lagunitas Creek, and an obvious final rest point before cycling into San Francisco, as it's about 25 miles north.
We also heard good things about Elk Prairie campground but it didn't fit in with our mileage schedule.
When you get the ACA maps, make sure you get hold of the latest amendments. Some of the updates are fairly trivial (e.g. campground changing name slightly) but there are also some useful corrections, e.g. "turn right at Ocean Drive should read turn left", etc.
Charges: Oregon h/b sites were around $6 per person, Californian ones $5 (but $7 for Salt Point with no showers!) Showers tended to be free in Oregon but required a few quarters in California (something like 50c min. for 2 mins).
It's a great route, enjoy!