YOUR "dry conditions", Melissa, are -- ummm -- outside most gardeners experience. When most of us talk about roses -- once established -- surviving periods of drought -- we're talking about places that do get winter rains, and some moderation of temperatures. Myself, I wouldn't try to grow roses in your conditions -- and if I did, I would have to learn all over again. (But then, if I moved to Wisconsin, or Louisiana, I'd also have to learn all over.) I have learned not to give advice to those whose conditions sound radically different from my own. I plan to stick with that. Let me just say that I have seen old rose plants survive for decades with no care, and no summer water -- living through dry summers in a state of dormancy, and reviving with the onset of winter rain. They may not bloom much, but they have survived. This did not happen in deep desert. It happened in Northern California, in some parts of Southern California, and in the Sierra Foothills. Below, see what such a Tea typically looked like, after a hot dry summer, and before the onset of winter rain. In more recent years, many of those old survivors are disappearing, (I'm fairly sure the one shown below is) as our winter rainy season has diminished. And that's a sad thing.

Point taken about how not all of California is a Mediterranean climate, certainly there are deserts and high elevation mountains as well, which are not classic Mediterranean climates, but are still influenced by one. As you noted, the OP is located in a part of southern California that is squarely within a year round growing climate, so I was directing my comments to her situation. On the other hand, even interior southern California mountains and the Sierras are more similar in rainfall patterns to coastal Mediterranean conditions; we don't get the bone chilling winter cold nor do we get the summer rainfall, but instead just less frequent and less intense thundershowers. So the point I am making with regards to plants selected for New Mexico conditions, is that they won't always be the best fit. As to the need to cultivate soil to an 18 inch depth, I still think it is an outmoded approach, and would only advise a client to even consider it if they knew they had caliche or heavily compacted subsoil due to home construction, and would then suggest they do some deep drilling to break through the caliche,(for deep rooted trees only), or have the soil ripped if this is feasible to improve the drainage and they can afford it. Otherwise I think it would be much more efficient to mound the topography to get the required drainage and soil depth, and use the top dressing method of organic mulches and soil amendments to be renewed every few years, and let the soil bacteria and earthworms do the work of creating a better soil profile. As Al also alludes, it is much easier to plant smaller plants at the right time of year to work with the soil conditions, rather than force the issue and try to establish new plants in bone dry clay soils in the middle of summer; in my opinion it is just foolish to think they will get off to as good a start as anything planted to work with our rainy season and cooler weather. Not to mention that it will take a lot more water and regular attention to establish a new native plant planted outside the rainy season window of planting opportunity. If you want to till the soil to an 18 inch depth, and have the energy to take this on, feel free to continue with your approach. My take is that there are easier ways to landscape that work just as well, and take less resources of personal manual energy or mechanical energy to accomplish. I don't think there is any question that late fall into winter planting, no soil amendment or cultivation, planting out from smallest size possible and mulching heavily and supplemental watering as required the first several years can accomplish the miracle of catching up to larger sizes,(0ften as quickly as 3 years), with more intensive manipulation of the soils and more water for things planted outside the winter rainy season, and this process more closely replicates how nature actually does it in California situations. Now if you are talking about plants that require more water retentive yet also well drained soils, additional depth of soil amending may make sense, but to generalize and say that it is always better or required is not necessarily true. It is often illuminating to find that plants from one part of the world where they are subjected to seasonal flooding may in fact prove to be fairly good candidates for rather drought tolerant plantings here in California. A couple of examples from South Afica come to mind; such as various species of Kniphofia/Poker Plants, or Restios such as Chondropetalum tectorum. Plants are often more adaptable to situations outside the norm of their actual habitat than we would expect, but it also happens that there are others which are not...

To keep dogs off, you want something fairly substantial. Salal doesn't discourage my dogs, I can tell you that. They love to go crashing through it. Creeping mahonia does to some extent, and that's a local native also. Junipers and cotoneasters are good suggestions, just not the really prostrate ones. Something about knee-high is more likely to keep dogs off. Maybe creeping rosemary, or shrubby potentillas. You could also plant a low-growing hedge as a barrier, and then plant whatever you want for the ground cover.

hoovb, you'd be surprised, there are a lot of smaller trees suitable for 24" strips. That's the most common size in my town and they are home to many Crape Myrtles, Maytens, Eastern Redbuds, Flowering Crabapples, Trident maples, Tristania Laurina, and standard Photinias (probably my least favorite of the bunch and sadly they happen to be in front of my house). These are the trees offered by my city, so they are everywhere here. The key is it can't be a tree that gets taller than 25 feet. Interestingly enough, in my own town I've even seen people plant rose standards in these strips, and while I wouldn't choose that, it looks pretty amazing! But a rose bush would not be ideal, you're right about that.