The smaller sedum are nice and soapwort... do you mind plants that would hang/trail? Perhaps Black-eyed Susan "Vine" (I think I have the Latin for that one listed on my trade list to clarify better), morning glories (especially Japanese MG's and MGs could be planted at the base of the wall and climb up - plus they can self-sow and in your climate, you stand a really good chance of them being "extended" annuals), ivy (those that tolerate full sun) always look awesome against/on stone walls in my opinion... I know there's a "recipe" for taking existing moss and making it into a "paste" and "painting" it on (hrmm reminds me of a Chia pet hehe) and you could likely find a moss that grooved on full sun... Miniature luffa has a delicate vine and much smaller fruits than standard luffa and has dainty little yellow blooms.... I wonder what plant "forms" you prefer though and what colours - foliage and/or blooms... that would help to narrow down some choice selections for you. Hopefully you can avoid using chicken wire and get things in place without it... it can be a pain to get out once plants are established....

look at T. o. degroots sprire ... look for single leader plants.. and try to maintain them that way ... they will outgrow many of the other arbs.. like emerald green etc ... height wise ... and i would diversify the planting .. perhaps the holly gal mentions ... i would also plant at the bottom ... why not .. i would go no more than 4 footers ... ken https://www.google.com/search?q=Thuja+occidentalis+%27DeGroot%27s+Spire%27.&source=lnms&tbm=isch&sa=X&ved=0CAgQ_AUoAmoVChMI59iW_ampxwIVB0KSCh3LTgG7&biw=870&bih=745&dpr=0.9

I think it's unreasonable to think you'd need to go ALL the way down to original grade with fence posts in order to have a sturdy fence. What you do hinges on the strength of the wall which, of course, we can't gauge from afar. But it appears to be a solid, poured concrete wall, so likely it's strong and adequately stabilizes the soil for a fence erected nearby. In spite of that, it might be as much questions about other things that guide what you should do with the fence. The first of those questions would be appearance. Consider extremes in order to help determine what will be good. One extreme would be a fence directly on top of the wall, extending its plane. Since the retaining wall is a plain, unadorned, flat surface and a "modern" fence with horizontal elements is likely to look similarly hard, raising the height in the same plane is likely to start looking like a military installation, sending messages like: keep out ... off limits ... secret ... Bin Laden used to live here ... etc. To the contrary, stepping the wall back a few feet, is going to give a friendlier appearance. The next question to consider is the construction of the wall. A good retaining wall is built with a layer of drainage gravel directly behind it. Water is collected at the bottom of that layer and piped out from behind the wall so as to prevent pressure pressure from building up (and trying to push the wall over.) In the pictures, a border of gravel is seen at the surface of the back side of the wall. I'm thinking this is probably an extension of the drainage gravel all the way to the surface. Whether it is or isn't, it would be a good idea not to place the fence posts directly behind the wall where they would be in the gravel layer. Thus, there are two good reasons to step the fence back from the wall face. Given the scale of the property, I'd say a 3' set back would work well. I wouldn't go less than 2'. Might go 4'. If you want more specific advice, show the property from the curb, but lined up with the center of steps, and take slightly overlapping pictures that shows all the way from the left neighbor to the right neighbor ... so we can see the complete scene. Also, show a plan view of how the retaining wall is laid out on the property. I am not against the "modern" look at all but think you must consider how it integrates with its surroundings. It might be more modern looking if all the plants on and surrounding the property were vaporized and one created a look along the lines of a power company sub station ... like a desert of gravel and an engineered looking patch of grass. Hmmmm .... maybe that would be a little unfriendly looking ...? Actually, I think your modern-looking house looks fine with the trees and greenery around it. SHADE is a nice thing ... more friendly than blazing sun. Along these lines, I'm thinking that maybe extending your retaining wall with another hard, fairly plain surface, is going to be just too much hard and plain. Personally, it would be for me. Because something has a friendly surface does not mean it contradicts compatibility with "modern." To the contrary, I think a friendly surface has the ability to HELP modern look better. One such example that comes to mind is how creeping fig can cover a wall in greenery, while at the same time looking very "modern." Here are examples (one of them doesn't qualify as modern.) I'm not suggesting creeping fig, but using it as an example of a "look" that is compatible with "modern" but still not unfriendly. Even if a "hard" fence is used, I think there must be something interesting and friendly about it.

Can I plant a palo verde desert museum behind a retaining wall, and if so, how many feet back does it need to be planted? Below is a picture of the type of retaining wall I have.