For your purposes and location, I would think a species that was quite drought tolerant would be more appropriate. Even these would require regular irrigation initially to become established but the too frequent need for ongoing irrigation seems slightly environmentally irresponsible as well as counterproductive to the other plants selected. The red fescue has lower water requirements than many other commonly used turf grasses but it is considered a cool season grass and will want summer dormancy in your zone. And a dry dormant grass will be a bit of fire hazard.

The carex is a moisture lover. An alternative could be Carex tumulicola or Berkeley sedge. It is used extensively as a lawn substitute in Southern California and will tolerate drier conditions far better than most other carex. And it will provide a very attractive, undulating meadow look.

I don't know how common it is in your area, but buffalo grass, Buchloe dactyloides, is another possibility. And relatively easy to grow from seed. I know it is highly recommended by UCDavis as a very drought tolerant alternative to other commonly used turf grasses for the south coast and high desert areas. Look for 'UC Verde', which was developed for the area by the University of California.

Gardengal48, what a great and thorough answer!
Since asking the question I purchased two more Ceanothus and two Acaias. I planted the shrubs but held onto the Red Fescue seed and decided to ponder a little more. I like Berkeley sedge and have it growing in an irrigated part of the yard.
I'll research the buffalo grass as you recommended and then should have all the ammunition I need to make the right decision.
Thanks again for taking the time with your well thought out answer, I (almost) feel you should get your consultants fee on this one.

Hope it was helpful, Richard. I have family in the south coast area and visit often and I've done quite a few landscape designs for that area. I'm working on one now in Dana Point. Your ongoing drought conditions and the recent fires (I left SoCal the day the Mailbu fire broke out) has made me rethink a lot of landscaping options. I am particularly interested in the "California Friendly Gardens" program that is being promoted by various nurseries and water districts in Southern California to encourage selection of native and very drought tolerant and fire resistant plantings. If you are not familiar with it, it's worth investigating.

If we had met in person, I might have handed you a bill, but on the 'net, it's all free!! :-)

I hope you'll reconsider planting the Acacias - non-native and terribly invasive in your area. If you'd like to plant a sedge, consider Carex pansa (Sand Dune Sedge) native to your area and loves sandy soils. You might also try Salt Grass (Distichlis spicata), a warm-season grass that can even be mowed. If you are more interested in ornamental native grasses try the native Needlegrasses (Nassella cernua and N. lepida). Deergrass (Muhlenbergia rigens) is not native to your immediate area, but is very attractive and will probably do well in your situation. You might also consider Pacific Coast Strawberry (Fragaria chiloensius) which also covers well on sandy soils.

Some larger growing grasses/sedges that are native to southern California would also work well as filler between the shrubs. You might consider using Eleymus condensatus 'Canyon Prince', which slowly spreads to form large clumps, has lovely pale blue foliage and can get 4 feet tall. Various Juncus species such as Juncus patens(bluish foliage) and Juncus effusus or Juncus 'Carman's Japan' are both in the 2 foot height range and a deep green color. Juncus are well adapted to both wet soils and drought, and are best planted to establish in winter.

The Carex species such as C. pansa and C. praegacilis are both not ideal on slopes with clay soils, and would probably need more irrigation than you are wanting to give them. Carex tumulicola is easier to establish, but still is likely to look better if given more water and some shade.

As a complement to the shrubs you already have on this slope, and as a faster filler to cover the slope, you might also consider using some fast growing Salvia species as filler/ground cover. Salvia clevelandii would work well, as would S. leucophylla 'Pt. Sal Spreader', which has great gray colored foliage and can spread quickly to form a shrub 8 foot across. You could also use the common Monkey Flower, Mimulus aurantiacus, which is a drought tolerant, low spreading herbaceous shrub native to the Santa Monica Mountains. Another great herbaceous perennial for southern California beach areas would have to include Erigeron glaucus and its hybrids and cultivars.

You might find that adding automated drip irrigation for this slope increases the growth rate and ease of establishing anything you plant, as hand watering is unlikely to be getting water deep enough to really encourage deep rooting on a slope. Getting things planted now, in January is the best time to get anything out there established with the winter rains and cooler weather.