George I lived in Murrieta until about ten years ago. Now I am in a similar climate In Sun City. Every once in a blue moon we'll get a cold snap in the 20s that kills everything but most years you can overwinter tomatoes and peppers. If they are already in containers you can move them to a Southern exposure with overhang from patio is perfect. The low Winter sun will keep them alive and, depending on the variety, they will ripen fruit. I have several tomato plants growing right now. They will not take nearly as much water during the cool winter months as they did when it was hot. It is very easy to root tomato cuttings in water or potting soil. You might consider doing that to start with fresh plants in in the Spring.

Don't do "one plant per container" unless they are very very close. The plants need to pollenate each other. Do use Ray's EarthTainers and plant multiple plants in each. Add water and you'll have happy pretty corn like in the pictures. If you get the black smut fungus, contact me. It's a delicacy! But you are not likely to have the fungus using the containers and good new planting mix. Rick Here is a link that might be useful: EarthTainer

Fig and pomegranate are best planted when they are dormant -- Jan-Feb is good. It doesn't matter whether they are bare-root or caontainerized. Fall planting is, as you say, "okay". Avocados are best planted in late-winter-earliest spring -- Feb-Mar is good. Joe

Unfortunately, that width is probably going to limit you :-) The elevated nature of any above ground container exposes it to much colder temperatures than a plant would experience in the ground. Especially the roots, which are far more vulnerable to cold damage than the top growth with even very hardy plants. But the larger the soil mass around them, the greater the insulating factor, so with a large container in a moderately cold zone you can often get away with overwintering plants that would likely not survive in a smaller container. Pretty much any tree or shrub you may choose will easily produce roots that fill up that 10" width, resulting in a root system that will very likely come into contact with the planter walls and therefore be exposed to excessively cold air temperatures. And root damage (resulting in plant death) can occur at temperatures as mild as the mid 20's, depending on species. And you are looking at the possibility of below zero air temps in zone 6 :-(( You might be able to risk it with the selection of some hardy dwarf conifers but they tend to be expensive to use in what is essentially a hardiness experiment at best. I wouldn't recommend any flowering shrub or tree except perhaps something like alpine currant, as the root system will simply get too large too fast. Unless you are inclined to toss money away on this experiment, I'd stick to seasonal plants. You can always stick in cut willow stems or redtwig dogwood stems together with cut conifer greens and hollies if you want some winter interest.