I lived in San Clemente (Most southernmost city in Orange County) for over 30 years before moving to Lake Havasu City Full time in 2012 and I can say that the riding there is pretty hard to beat (Weather wise). OC Harley has a very active HOG chapter but I am personally NOT a fan of 100 bike rides.....especially with such a high percentage of the riders being new riders....recipe for disaster and I know from personal experience
I suggest that you might want to try a ride or 2 with the heard and try to make some friends for a more comfortable 2-5 bike ride with like minded and capability riders.
As mentioned Ortega highway is always a good ride and there is a cool place to stop for lunch there named "Hells Kitchen" which has the coolest condement dispenser to be seen at a "Biker Bar"......there is also "Cooks Canyon" which is always the scene for 100+ bikes to stop on any given weekend and they almost always have a live band.
Heading south toward San Diego there are some great rides down to Mt. Palomar, around Lake Henshaw and the Julian is a great place to ride for the day as well. You can ride and ride and ride in that area almost exclusively with great weather year round....except for maybe those 10 - 15 days a year
I personally got out of there because I got tired of all the BS in CA not to mention the cost of living now that I'm not making the big bucks anymore but I wouldn't give up all the great years I had there for anything.....good luck with your move!