I hear Route 1 can be a bit hairy, especially as far as shoulders are concerned. Is it an issue?
If you ride in NYC, you will really enjoy Highway 1. I rode that stretch the same time you are going to be doing it. There were some jerks who yelled at me for riding in the road when there was no shoulder, but if you are a cyclist you will be used to that. Depending on your mood, you either shrug it off, or give them holy hell back. On weekends, there will be more traffic and more jerks. But you will only notice the traffic during the short sections where the shoulder disappears. The road is 'hairy' in that there will be a small shoulder, then a low rock wall, and a cliff that plunges 100 feet down to the rocky ocean. I found it to be 'spectacular', rather than 'hairy'. There are pullouts every so often, so a patient driver will be able to get around you at some point.
The ACA maps are great because they list all the 'hiker/biker' campsites along the way, as well as which towns have grocery stores and bike shops. The hiker/biker camping works like this: it costs $10/night in CA (in Oregon it's only $5/night, but with CA's budget woes, they doubled the fee), and the hiker/biker site is usually a group site with a communal fire place and some communal picnic tables. Showers are usually available--but not always. In the height of summer, the hiker/biker sites are never at full capacity, and every camp host I ever talked to said they would never turn away a hiker/biker--they would squeeze your tent in somewhere. So you don't need reservations, and I don't think they take reservations anyway.
Because of CA's budget woes, the state announced closures of some campgrounds along the Pacific Coast. Someone posted a list on these forums, and I'm sure you can find the list elsewhere too.
I found the Oregon coast to be much nicer riding, it had better campsites, and it was more beautiful. The state of Oregon also publishes a free bike map of the coast route with all the hiker/biker sites listed. I was pretty disappointed with the California coast and the camping. So if your plans are flexible you might consider Oregon as an alternative.