North of San Francisco, Hwy 1 is just plain awesome. Tons of stuff to do and see. Very curvy road, but worth it. Hwy 101 at that point is not as hard to drive, but not much to see.
On 1, there are a few State campgrounds and hundreds of private ones. Not too expensive, especially this time of year.
Bodega Bay. Lots of cool restaurants and you can still find some of the areas where they filmed Hitchcock's The Birds. Not all of it filmed there though. You'll have to look that up.
Fort Ross. State park and historical Russian Fort. $6 to park, but walking around is free. They fire off the cannons occasionally and have some of the rooms in the fort set up as they'd look originally. The Russian Orthodox Church there still holds services every Sunday.
Point Arena. Best pizza in the world at the wharf and great ice cream. There's also the B Byron Preserve. Not super cheap, but an awesome place. You get in a safari truck and they drive you around to see African animals on the preserve. One of the best experiences my family has had. Probably best to unhook the trailer in town somewhere before driving in. Some cool antique shops there too.
Manchester. My favorite camping spot. And favorite beach. There's a state campground there, just past the KOA where I usually stay. Follow the signs off the hwy to the KOA and just past it, you'll find the state park. Keep driving and there's a large parking lot for the beach.
Mendocino. Lots of great shops and restaurants. This being a larger town, check to see what's going on. Usually some type of art or wine festivals can be found almost year round. Not sure about camping here, but I'd be surprised if there wasn't.
Fort Bragg. Capt Flynn's down at the Marina has some of the best food you'll find, at a great price. Small quaint spot. Last time I was there, they still only took cash (lots of places like that on the coast, be prepared for that). Glass beach is very cool. Look up the history, then go check it out. Try to be there during low tide, lots of tide pools to check out. There's also a free tattoo museum in a working tattoo parlor. Very small, but even if you're not into tattoos, it was a very cool little place. More history than anything else. The Skunk Train. That's not cheap, but if you have a day to kill, take the halfway trip. Very neat historical train with a conductor that talks about history the whole time. Well, worth it.
Weather up there can be cold, wet, warm (never really hot), and dry. All year round. Dress accordingly. Gas is about as expensive as you'll find. Fill up in the more major towns to avoid the worst of it. Park where you can to take pictures between towns, this is some of the most beautiful coastline you'll ever see.
That's all off the top of my head. Hope that helps.