I assume you are looking for an event ride - like a century with options. Here are some suggestions which then also provides resort lodging and other ride options:

Cool Breeze Century - August - from Ventura to Goleta and back. See cibike.org for other ride options.

Palm Springs Century - February - obviously lots of resort lodging and lots of ride options.

Cruising the Conejo - May - N Valley/Camarillo area.

Big Ring Century - June - Orange County. This was the first year and hopefully there will be a next (so its still very small). It's a nice route (one I do parts of alot) and you can't beat Orange County for weather/lodging/route options. More info on OC routes go to bikeirvine.org or ocr.com.

I will have to check further on San Diego rides - San Diego is the area I would recommend just if nothing else, how nice the area is and with lots of ride options.