I think they like full sun. You'll also need to be a little careful with it--they tend to be a little borderline for zone 9 (at least up here where I am--maybe your winters are slightly warmer than mine since you're in SoCal?). As far as needing more than one tree, I had one at my old house and it did give me a few fruit all on its own, but if you're growing this tree in the hopes of having avocados to eat, you might want to get a second one (of course, I didn't really fertilize mine either, maybe if I had done that it would have given more fruit too!). I don't know what kind of avocado I had, there may be some kinds that require a 2nd one for pollination. As far as soil, I can't really advise you there--mine was a huge well established tree that came with the house. You do also have to be careful with watering--if mine got watered too much it would start to drop some leaves. When it's young and not established it'll definitely need watering, but once it's older make sure you don't give it too much.

thanx for the input....by the time I "find" enough to buy a sapling, I should have at least a small clue......thanx to places like GardenWeb

I'm not an "expert" but take care of several thousand trees.

They like full sun and are fast growers. They survive in part shade but will get tall and thin with lots of twig dieback if sunlight is limited. They prefer temperatures from 32F to 90F, some varieties will survive brief frosts after established. Extended high heat like this past July (100F+), can sunburn new leaves and branches. Easiest way to tell if your location is OK is to look for avocado trees in your neighborhood and see if they are doing well.

Well-draining soil with lots of organic matter is important else they are prone to root-rot disease. Most in southern CA are grown on steep hillsides that drain well. Lots of water, let dry, then lots more water. I put nearly 500 gal per week on mature trees (40 to 60 ft. tall), about 60 gal per week on one to two year olds (3 to 10 ft. tall) in summer months.

I usually wait until early spring to plant because the survival rate is higher if planted just before their growing season, although a single tree should survive as long as it doesn't freeze and you give it the TLC it deserves!

As far as pollenation from two varieties (A & B blooms)... there are as many opinions on this as there are growers. I believe that if you have bees and wind, you'll be fine with a single tree. I eliminated all my pollenators 3 years ago and have seen no decline in fruit.

Hope this helps...