I'm not a big shade gardener, but I know hostas are shade loving and easy to find and to grow. Some rhododendrons like shade, but might be harder to grow. Do a search for shade loving plants and you should find a lot. --Kris

There are some really good shade plants that grow well in your area. Hostas, of course. Crepe myrtles and dogwoods are understory trees that are shade lovers.
Oxalis, mandevilla (they grow well in partial or full shade) soapwort, impatiens, azaleas.
You might want to go to highcountrygardens, or Guzman's Greenhouse on the web. They have some greatshade plants that do well in Southern California.

Here is a link that might be useful: Desert Gardens

Here in southern California, most of our soils are naturally dry and alkaline so I'd steer clear of acid & water loving plants such as azaleas unless you plan to manipulate the area heavily. One trip to a California native nursery should supply all your needs for a small patio garden. Las Palitas Nursery has a wonderful web site describing native plants for specific situations.

Maybe use Berkely Sedge (clump grass) as a ground cover along with seaside daisy if you have semi-shade. Native Maidenhair fern would soften edges and you could add some interesting California succulents/dudleya, depending on exposure (some sun?). You might want to consider planting a narrow patio tree such as the Catalina Ironwood if the top of the tree would have sunlight. If not, a vine (native Chaparral Honeysuckle) growing up the fence could be used instead of a tree.

A trip to a nursery specializing in California natives will save you time and money needed to change soil and moisture to support typical acid/water shade gardens.