If you'd like to learn more about native plants for your garden, here are several great local resources that I recommend:
I suggest Rubin & Warren's California Native Landscape to my clients just for the section on landscape maintenance. This book also has a nice introduction to garden design and wonderful photos and descriptions of lots of native plants for your garden. Greg and Lucy are both leaders in San Diego's native plant community.
Moosa Creek Nursery is tucked away near Valley Center in north County, but they have a network of retail nurseries around the County where you can see a selection of popular container plants and pick up your order.
Their website is a good source of information on the water, sun, and drainage requirements of their plants -- if you can correctly spell the name of the plants you're interested in.
Native West Nursery started out supplying plants for their parent company's restoration projects, but they have gradually expanded their plant selection and now include cultivars for gardens. It's a wholesale nursery, but they have a public Fall Plant Sale, just in time for planting season. If you live in south County, you should attend the sale and take a look at their operation. Their address says San Diego, but they are practically in Imperial Beach.
Tree of Life Nursery was the first native plant nursery south of LA and remains the largest. Located in the foothills off the Ortega Highway east of San Luis Obispo, it's worth taking a day trip to OC to browse the bookstore, check out the straw bale buildings, and walk trails through a park-like setting.
Their website offers a downloadable catalog of their plants with succinct info on their species.
California Native Plant Society - San Diego Chapter hosts monthly meetings with speakers on topics ranging from taxonomy to conservation to gardening. Become a member and get Fremontia, the CNPS magazine, go on botanical hikes, or volunteer on one of many committees.
The Fall Plant sale has been a tradition for 40 years and is a greast opportunity to talk with horticultural experts and pick up a few more plants for the garden!