Agaves of a number of species would fit the bill - Aloes, too. Aloe arborescens would do well, but as you likely know it's pretty common - maybe that new hybrid from the Huntington Garden 'Vulcan's Fire' or something like that?

Brad (paracelsus) might have some ideas for you of what does well in your area. The Ruth Bancroft Garden (home of Brian Kemble, Aloe and Agave Man Extraordinaire) would be an ideal source (and you'd be helping out the plant cause, too).

I have Senecio vitalis and Senecio barbertonicus--they form rounded shrubs about 3x3, like a boxwood. Very shrubby indeed! The vitalis is blue-green, and the barbertonicus is very green and could be mistaken for boxwood at a far distance. Very easy from cuttings, you buy one plant and grow the rest from cuttings.

Though once established, tough, basic shrubs like Ligustrum, Boxwood, and Myrtle are very drought tolerant and get by on modest summer irrigation and no irrigation at all in winter and spring. I have some Myrtle I don't water at all except a couple times in summer, and it's thriving and beautiful.

Another approach would be a native shrub such as Carpenteria or Coffeeberry. Again, once established, as water-thrifty as any succulent plant.

Do you have invasive issues with ligustrum in California. WE do in Texas. Those birds love and carry the seeds everywhere. City parks, especially the large wilderness preserves fight this issue a lot.

Sunset Magazine's display garden is around Palo Alto. You might take a trip there for ideas.