I just added my zone to this.

No-mow grass is not very attractive - kinda weedy and unkempt. And it still requires regular irrigation to look even half way decent, which may be an issue in many parts of CA.

Attached is a link of suggested groundcovers for your area, including a number of native species as well. Just pick for your specific sun conditions and an appearance you prefer. Personally, I'd put a big emphasis on fully evergreen and drought tolerant - the manzanita, ceanothus, junipers and rubus all fit that description. All are very appropriate for slopes also.

Here is a link that might be useful: groundcover suggestions (pdf)

I like gardengal's evergreen idea. Pinus sylvestris 'Hillside Creeper' (sounds like a murderer, but it's a plant) will survive up to Zone 8 and cover a lot of space. It gets 1-2 feet high and 6-8 feet wide. It is, however, rather pricey, so it may be out of your budget.

Groundcover roses are also drought-tolerant once they're established. So if you wanted to sprinkle in some color, you could.