I hope you have resolved by it now. We have a hill in the back yard as well and I was looking on here for ideas. I would mix some stones into it (as simple as limestone rip rap)to help slow down the erosion. Mix some topsoil in. Sow some sunny wildflower mix seed. Maybe even make a few paths and small sitting area that will draw you up there. A bird bath maybe. Keep it low maintenance. I hope that wall has some drainage. Hills are for heroes.

Those wildflowers at the top of the slope look like mallows of some kind, maybe Lavatera. I like your palm tree. Looks like Trachycarpus. Very hardy and has flowers when it's taller. It also drops fronds, but not often. What you put on your bank really depends on how much time you have to stay on top of the care needed for the first year or so until any plantings get established. There have been some lovely suggestions offered already: the iceplant and the local Ceanothus. There are varieties that spread beautifully to smother. Otheres are taller and more bushy. They come in a small range of colours, mostly blues and purples and they can provide a succession of flowers over weeks. I liked the idea of the California poppies. They are so tough! And there are colours other than the standard 'orange'. You might want to plant 'pools' of them among Ceanothus to give a fairly strong visual impact. A 'Pacific' colour scheme suitable for strong sunlight. Pastels tend to get a bit lost in hard light. The iceplants can be very effective - big sheets of colour usually in 'hot' tones, although there are softer pinks available. And, for seriously tough sites - Gazania, Arctotis, Anigozanthis (kangaroo paw - which comes in a pleasant range of flower colours dark red to interesting green.) They're usually perennial. Climbers and sprawlers - Bougainvillea, Campsis, Trachelospermum (which smells delightful). Instead of climbing a trellis they can sprawl down the bank, needing only a trimming with shears to stay civil. Bougainvillea has thorns, however. As do the carpet roses and Rosa 'Nozomi'. That's a fairly steep slope so work across it rather than 'up/down' to reduce the risk of rain damage. Leave strips of grass to catch the run-off and protect your pool from mini-mudslides. At least until your plantings are spreading out. Before planting ANYTHING - check with your local garden centre to see if it's safe for newbies. Some things look so innocent when you see them as a cute little cutting in a teeny pot... and then you find they have rule-the-world tendencies. English ivy would be one. Cortaderia would be another. Many South African bulbs, such as Watsonia, can happily fill acres. So can Ornithogalum. And, if it's not too hot where you are, asparagus fern and ginger plant can take over in no time. If you should chance to like them - and don't mind some spiny-ness consider bromeliads. There are many hardy varieties that happily live outdoors, flower fairly regularly and make a good groundcover. And aren't fussy.

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.

The slope looks like a similar area that was on the undeveloped adjoining property. This area was placed such that it made my yard look bad. The first thing I did was go in with a brush blade on my trimmer, and cut every thing down. Once the area was at a height that I could see what was there, I went in with a mattock and cut out every thing that would damage the mower and leveled all ruts so I could mow through them. From then on I mowed the area with my lawn mower. After a couple of years of mowing, from a distance, looks like a nice lawn. The slope look like it is less that the slope in front of my house. I mow it sailboat style, sitting on the high side. If time is a problem and you are not working under the "protection" of the city, I would start by cleaning and mowing a couple of strips on the side walk side. Then over a period make one or two more passes up the slope until I was up against the fence. In this way you will be able to study the area and correct any problems before you get into it with the mower.