Hello,
I am new to this forum and somewhat new to San Diego bicycle riding and want to make some suggestions based on my San Diego bike experience since November 2010.
I sailed my 40' boat from Puget Sound to San Diego in September 2010 after one too many wet&cold Puget Sound summer time rides (I have lived in B'ham/Seattle/Tacoma since 1965 and have been a serious rider the entire time). I got my mountain and road bikes down to the boat in mid-November and felt like I had died and gone to bicycle heaven! I have been living on my boat in San Diego since late January and ride almost every day (3 days/week hard mountain biking & 3 days/week of 40+ mile road rides).
Most of my riding is south of Encinitas but I have done some stuff north of there.
You can find $39 - $59 hotel rooms in Hotel Circle (I-8 between the 163 and I-5) and in the Midway area (just east of Ocean Beach and south of I-8) - at least that is what all the signs I see there say. It is a 20 minute drive from Hotel Circle to Encinitias / Rancho Bernardo / Poway / Chula Vista / Otay Lakes (i.e. pretty convenient to all kinds of riding)
I don't do group rides anymore - I prefer to ride by myself or with one or two close friends. I had no trouble finding dozens (maybe hundreds) of great rides. I used several online websites (e.g. MapMyRide shows 969 rides in San Diego county) and talked to several bike shops (Performance in Midway was very helpful with routes). There is also a very good paperback book of road rides (Cycling San Diegon by Nelso Copp & Jerry Schad $11 at Amazon) - I found it it be accurate and useful with good elevation guides.
I'd suggest riding by yourself and exploring beautiful San Diego county at your own pace on rides that interest you.
A coupe of observations about San Diego by a very experienced but non-San Diego rider
1) It is impossible to ride more than 20 miles without climbing several 300'+ hills
2) It gets pretty steep pretty fast east of I-15
3) San Diego car drivers are very considerate of bicyclists - I've ridden in many places and San Diego seems best
4) It gets REALLY hot east of I-15
5) Riding North-South along the coast (west of I-5) stays nice and cool with a consistent afternoon sea breeze
6) The scenery east of I-15 is astounding - I love desert hills and valleys and love to ride east from Escondido / Santee / Poway / Rancho Bernardo
7) There is a lot of interesting riding SE of San Diego (Otay/Jamul)
8) ANY road with the name "valley" (e.g. Highland Valley) in it is certain to climb/descend hundreds of feet every mile as it goes over ridge after ridge
I plan to spend most of next winter riding in San Diego before I head south to Mexico (2001 - 2004 on my boat in the Sea of Cortez and used my mountain bike to explore hundreds of miles of desert trails)