I’ll second Roland’s comments. There are several native species found in the Bay area that also grow naturally (and unnaturally) in southern CA – look at what’s growing in your local natural swales and try using some of them. Also, aside from stormwater filtration, does your proposed bioswale have any other purpose, visual or functional?
Finally, you might want to talk to Rana Creek (http://www.ranacreek.com) – I think they might have worked with your firm before, and they certainly know their stuff where sustainable water management issues are concerned.
