I'd take Sissoos over Mesquite. Sissoos grow extremely fast if you are looking for fast growing trees. I also like Chinese Elm. Not necessarily fast growing, but I like the look. I have all 3 growing and a few others. I have vines growing along my fence - I don't know what the name of it is, but it branches out all over the place and has hundreds of yellow flowers! I also have very leafy, ground covering plant in front of my house that puts out both white and yellow flowers - lot of them! Likes water, though, especially during the summer. I can get the name of it from Whitfill's are interested, though the vines I have no clue, got them at a nursery that was going out of business. I am also experimenting with growing a Queensland Bottle Tree (not to be confused with other Australian type of bottle trees). I was at a house that was in a pond club that was doing a tour of homes with Koi ponds. One of them had a couple of these trees that had grown to 20 plus feet. Absolutely gorgeous and extremely different than most anything else you find around here and it loves Phoenix weather. If interested, there is a seller on Ebay that I bought mine from. They aren't exactly fast growing, but it's a project tree. I'm not a fan of palm trees, just my preference. They grow "wild" on my property and I have to pull them out all over the place. There is another type of desert tree growing on my property that I didn't plant but let grow. I have no idea what the names of those are, either. One of them is 3 years old and about 21 feet tall. Beautiful tree and actually gives some good shade. I saw one at a museum that they had planted a few years back, but I can't remember the name of it. I would also suggest thinking about pine trees. They are ever-so-slow growing but they can take whatever weather this city can give it, unlike my Ficus trees which sustained major damage in the recent extreme frost session we went through. I was lazy though, I could have saved them - wrap C-9 Christmas lights throughout them, especially on the tops if you can get to them and the heat coupled with covering them up does a nice job of helping them weather extreme cold. Yes, I have in the past wrapped C-9 version of Christmas lights around certain plants and trees that are susceptible to extreme cold when the forecast is for hard freeze and yes, it works. May I also suggest a Koi pond? Just for fun. Try starting with a small, preformed shell and see if you like it. Get some Koi and goldfish. They're fun to have! Small ponds don't take a lot of work and the fish learn to know you and the Koi will even come up to you! They survive the heat and the cold. I have one I made out of horse trough and 2 more that are preformed. I haven't delved into the larger type with liners - just haven't got there yet. Whatever you end up doing, have fun with it!

Also, we need to put a small retaining wall on left but it doesn't need to go the whole way down..wondering if I can incorporate that into fire pit and make a bench.

Consider creating terraces. Decide how much room immediately behind your home you eventually want for a backyard patio. Leave at least six feet beside each fence not dug but dig a ditch/footing for a wall of concrete block down to hard ground across the center of the rest of the back yard. Once your terrace wall is built, level the area above the wall, including by adding a truck load of gravel and/or dirt and/or shoveling dirt from below the wall to above it to level both your patio area and a space below the wall. Once you've reserved your patio space -- while your dogs pack it from using it -- you can begin to plant your garden, preferably in a way the dogs can be taught to leave what you plant alone. Pay attention to how the sun passes over your back yard so you're not planting anything that will eventually shade your garden too much for it to grow. Brackets on fence posts can hold potted plants -- choose the strong ones. https://www.google.com/search?q=very+strong+bracket+for++holding+flower+basket&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjy1KW5l4LoAhWiSt8KHRZkBw0Q_AUoAnoECAwQBA&biw=1366&bih=628 Consider the stronger tomato cages for tomatoes and beans. You can buy individual trellis/cages in the spring from the big box stores or build your own -- there are You Tube videos on how to build different kinds. This is just one. https://www.youtube.com/watch?v=ozQNsd5Oek4  Consider building a mini greenhouse using plumbing pipes and/or wood. https://www.youtube.com/watch?v=KsSI4w3CqEo https://www.youtube.com/watch?v=sQWPnaiixe0 https://www.bing.com/search?q=building+greenhouse+with+pvc&form=EDGSPH&mkt=en-us&httpsmsn=1&msnews=1&plvar=0&refig=d03dc932a900445e84174ddd49ea6bb8&sp=1&ghc=1&qs=AS&pq=building+greenhouse+with+&sk=PRES1&sc=8-25&cvid=d03dc932a900445e84174ddd49ea6bb8&cc=US&setlang=en-US If you build raised beds with wood, remember to line the wood box with plastic to make the wood last longer. https://www.youtube.com/watch?v=ef_TS19TRQg and / or building tiered structures for plants https://www.google.com/search?q=wood+tiered+structures+for+planting+strawberries&tbm=isch&ved=2ahUKEwiv8fyvk4LoAhXEEFMKHS1JBKMQ2-cCegQIABAA&oq=wood+tiered+structures+for+planting+strawberries&gs_l=img.3...95448.101579..102697...0.0..0.134.1724.15j4......0....1..gws-wiz-img.NbM-ukJ-fRs&ei=qFFgXq_9FcShzAKtkpGYCg&bih=654&biw=1366&client=firefox-b-1-d#imgrc=irj20Wqm9lLhnM

This is generic and organizational, not about specific plants. Not knowing the general direction you want to take with plants, Iook more at plant heights than what a plant might tend to resemble. For instance, what looks like grass might be gravel if you're going hard xeriscape. It could also be fake grass (but that's not cheap.) The small tree made out of a large shrub would be useful to you for screening neighboring properties. You might want to expand the patio in the future.