A noob here.
1. When's the best time of the year to do this?
2. What route is the most scenic/best/rewarding?
3. Assuming an average rider, how long would it take?
4. Any nice campgounds along the way or go the motel/hotel route?
The weather is best in the fall. October tends to be better than September.
Tourists drop off sharply after Labor Day.
Most people just ride down the established route; but there are lots of interesting and beautiful sidetrips and alternatives.
There are many hiker-biker sites for camping.
Most people try to make miles. A minority, though, make it a point to take their time instead. This couple describe their experiences with a slower pace,
http://www.youtube.com/watch?v=1oGOM...eature=related
http://www.youtube.com/watch?v=sR48g...eature=related
http://www.youtube.com/watch?v=tWZUT...eature=related
The bike path shown from about 04:43 in this video is well worth riding fully, and most people also enjoy the aquarium in Monterey:
http://www.youtube.com/watch?v=cV-Ng...eature=related
Making the most of the bike paths on and along the beaches, like the one beginning at about 03:07 here, is good (as is going through Malibu at some low-traffic hour and day):
http://www.youtube.com/watch?v=Yt7Cb...eature=related
http://www.youtube.com/watch?v=PBhUvkGWV-M
http://www.youtube.com/watch?v=13DKkVhCqPs