there are a couple of good ones i've been to there but i can't remember what they're called
go to the clairemont park and i'm sure the locals will point you in the right direction
just googled shops in that area and came up with this lot,might be of some use.
San Diego Area Bicycle Shops
*
Action Cyclery, 9910 Mira Mesa Blvd # C, San Diego, CA 92131 (858) 566-3341
* American Bicycle Company, New Name: A&B Cycle, New Location 10147 Mission Gorge Rd. Santee, CA 92071 619-448-4106
* Bike USA, 7730 Ronson Road, San Diego, CA 92111 619-560-8666
* The Bikesmith, 1936 Garnet Ave., San Diego, CA 92109 858-274-4220
* Bicycle Works, 3655 Avocado Blvd, La Mesa, CA 91941 619-461-6007
* College Cyclery,16425 El Cajon Blvd, San Diego, CA 92115 619-582-6440
* Lakeside Bicycle Center, 12346 Woodside Avenue, Ste. N, Lakeside, CA 92040 619-390-5924
* Mission Hills Bike Shop, 141 W. Washington, San Diego, CA 92103 619-296-0618
* Lemon Grove Bicycles, 7388 Broadway, Lemon Grove, CA 619-469-9831
* Southbay Bikes, 1201 Highland Ave., National City, CA 619-477-1445
* Thomas Bike Shop, 1635 1/2 Fern St. San Diego, CA 92102 619-232-0674