We sometimes park up at the LDS church near the corner of Black Mtn. Road/Hwy 56 and go cycling from there on the nice paved path along the 56. You can easily cruise to Del Mar for a dinner, though you have to ride back up some hills on your way home. The same path goes the other way to Poway and Scripps Ranch, but I am waiting for the weather to cool off to try it.
Once the summer tourist season is over, riding around Mission Bay is very fun — you have to battle your way to UTC (Cmino Ruiz/Miramar/Eastgate/Gilman), then pick up the Gilman bike path. So is going up and down the coast (mornings are better, less windy. When it is windy, it ususally goes North to South.) We usually park on a residential street in Del Mar and go north from there. If you are in good shape, there are a lot of quiet, lovely roads in Rancho Santa Fe for longer rides.
We’ve been too busy with a baby (who rides in a trailer) to hang out with them but there are all levels of riders at the SDBC http://www.sdbc.org/
