I'm tempted to say, just get out and explore. There is good riding N, E, S of you, but the riding to the west is all wet. La Jolla is good for a slow amble. To the south you get into Pacific Beach which is good for beach style riding and lots of girl watching. You can continue that way on down to Mission Bay.

To the east, its large well paved roads, with some impressive hills. Just for the unique thrill you can even ride on the freeway! Get on the I5 North at Genessee and ride it to Sorrento Valley. It's legal between these two exits. Then you can return up the freeway in the other direction. But in Sorrento Valley, explore into the business park and you will discover the Los Penasquitos Nature Preserve. The main trail is fairly flat and easy and winds along for about 5 miles.

To the north there is more of the beach, the Torrey Pines Golf Course and State Reserve. This leads to Del Mar and its racetrack and Solana Beach(Watch out for Sharks). I'm sure you will get more good news. It's been a while since I was there and DG should have better info on what bicycle shops are there now.