Juliann, I'll post a site from the UK that has pictures of various types of gardens. This link goes to their Cottage Garden which they say is "contrived to look uncontrived". There are many other types of gardens there that might provide inspiration. Which plants you choose depends on which climate zone you are in. I'm in zone 3 so am somewhat limited in what I can grow. I'll post a pic of what I call my wild bird garden. It's an area in my large garden that has the birdfeeder and birdbath. I allow the flowers to go to seed for the birds so they self-seed. This area has changed over many years altho I initially seeded shasta daisies (the butterflies love them) and yarrow and planted a few established perennials. The yarrow seeds I planted were a mix of red, pink, and white, but the white resembles the wild yarrow we have so we pull it out and it's mostly now only tones of pinks and red. There are also Lamb's Ears because they seed all over my garden but I leave them in this wild area (the bees love them). There are a few other plants, a pink mallow that's 'weedy' but it fills the space and is quite pretty and we also have several lilacs here. Near that area there is also a drift of common old irises which we've allowed to spread. They are in the lower part of the rockery and I will eventually weed some of them out as the bloom time is not very long. If I were deliberately planting a wildflower garden I would not buy a wildflower mix as there could be invasive plants in it. I planted a mix about 14 years ago and still have Dame Hesperis (Dame's Rocket) altho pull out many every year and try to dead-head them ASAP before they seed. It's quite a weed in warmer climates. I would choose seeds of plants I like that are hardy but not invasive and mix them together. Another option is to plant in swaths with various plants and grasses hardy to your area. Keep in mind the moisture requirements of the plants as you decide. The area where I have shastas, mallow, and yarrow needs little watering and only a spring weeding so is easy care. Here is a link that might be useful: The Garden House

We live on a very steep, but rocky hillside and a previous owner put various terraces on it. Since winter is coming, and to prevent that hillside from slipping, plant a lot of creeping rosemary. Rosemary is drought tolerant. Our house is on top of the slope, but you risk a ton of mud from that hill. Our entire 1.5 acres are covered with about 12 automatic drip stations, so everything gets water 3 x per week for about 45 minutes. Junipers, as ugly as they are also are good for erosion. We have many. Thinking about distilling some gin from their berries... NOT! Trees: Olives are drought tolerant as are figs (once established). Pomegranates seem fine with little water too. There is also some kind of burlap sand bag ropes that will help hold back mud and water. The house across the ravine from us has it on their big slope.

Jeanne, this situation appears to me to be one where you would be best served and receive the most benefit from an onsite visit and discussion with a professional designer/consultant. An online forum, even with input from the few professionals that post here, is just not prepared or qualified to provide the sort of information and assistance you need, even with more detailed photos. Earth movement and grading, drainage and the safe and stable retention of hillsides and slopes are all pretty technical aspects of landscape design that require expertise to address successfully and that is best accomplished by someone with the proper qualifications seeing it in person and with a first-hand familiarity of the location, climate and soil conditions.

Be aware that Doug lives in the SE US, which doesn’t have nearly the water issues of southern CA, so adjust expectations accordingly. There will be Mediterranean plants and as GG48 mentioned California natives that will work well. I would spend time looking at lots of pictures of southern CA gardens to get an idea of plant density and plant palette that is used in your area. Here is a Houzz article I found that includes several low water CA gardens. [https://www.houzz.com/magazine/8-colorful-drought-tolerant-landscape-designs-stsetivw-vs~86440802[(https://www.houzz.com/magazine/8-colorful-drought-tolerant-landscape-designs-stsetivw-vs~86440802) While the designer linked below is in the Bay Area, it shows that some type of steps and access is needed, if for nothing else, basic maintenance. One set of steps up and then paths across the hillside periodically is necessary since a lot of foot traffic on an unvegetated slope will lead to erosion. [https://www.houzz.com/photos/ornamental-grasses-mediterranean-landscape-san-francisco-phvw-vp~766320[(https://www.houzz.com/photos/ornamental-grasses-mediterranean-landscape-san-francisco-phvw-vp~766320) [https://www.houzz.com/photos/ornamental-grasses-mediterranean-landscape-san-francisco-phvw-vp~766323[(https://www.houzz.com/photos/ornamental-grasses-mediterranean-landscape-san-francisco-phvw-vp~766323) Photo sources include the landscape photos here on Houzz, books from your public library, general internet searches, gardening magazines for your area. Start a file of photos of gardens and plants you find appealing, even if they aren’t planted on a slope. You can save ideas in a folder here on Houzz of photos found in the Houzz photos tab, but you can also upload photos from other sources. Regardless of whether this ends up being DIY or designed by a pro, having ideas of what you find appealing will help. As functionthelook mentioned upthread, you want to be aware of leaves, flowers, and other material that is likely to be shed by plants near the pool as anything that drops in needs to be removed. You may be able to find a list of pool-friendly (low litter) plants for your area somewhere on Houzz or elsewhere on line that you can use for the area near the pool. You say there is irrigation on the slope. Be aware that it may need modification to work well for the plants and the design you choose, and make sure that you know exactly where lines run before the shovel comes into use.