A California native plant garden is a tough thing to peg down: what do people really mean when they say native plants anyhow? Certainly, definitions fly from once-upon-a-time-it-grew-in-California-somewhere-but-has-been-bred-by-the-nursery-industry-for-twenty-years, to the purists who insist that it must grow in San Diego county without additional water or care once established.
If you fit into the purist category, most of the typical gardening tricks (such as soil amending, fertilizing, or watering during the summer) will not apply. California natives are adapted to our alkaline soils and would typically only be exposed to rain in the winter (and not much at that).
Because of this, if you want to go for a full native garden, I recommend working with a contractor who specializes in native gardens. My local favorite is Wes Hudson with North Park Native Plants. He is easy to work with and his prices are very reasonable. His goal: gardens that require no additional water after the first two years. Here are a few things he lists on his website as the benefits of gardening with native plants:
1) Local plants become a native plant community
2) Gardens with local native plants conserve water
3) No fertilizer is necessary
4) Native gardens are low maintenance/save money
5) Native gardens attract local wildlife
6) Local native plants look good together
7) Native gardens reflect the seasons
8) Many native plants are very long-lived
9) Native gardens foster a connection to nature
10) Local native plants promote a sense of identity