Arlington Garden, 295 Arlington, Pasadena, CA is a lovely place to take a picnic in spring and has a good range of native plants, augmented by mediterranean plants and a few succulents and cactus.
Beverly's garden at the Sam Maloof Foundation, 5131 Carnelian Street, Alta Loma, CA 91701 is definitely worth a visit because the use of unusual native plants is so successful, particularly in late summer and fall. Many plants have been chosen for their super seedheads and dormant color. The foundation website contains a complete list of plants in the garden.
The Theodore Payne Foundation, 10459 Tuxford, Sun Valley, CA 91701 has a nice native demonstration garden, and a nursery too.