In the winter with no leaves on the trees, you will get sun almost anywhere with the exception of the norhtside of the house since the sun rises and sets farther to the south. In the summer the sun rises and sets farther north so you will get more sun on the north side of buildings. It is also higher in the sky so it will cast a smaller shadow to the north of a building. Bulbs and native wildflowers bloom and do a lot of photosynthesizng before the trees leaf out. So they don't mind shade in summer too much. Most plants labelled sun/part shade do well in 4 hours or so of sun. I would expect your avocado gets enough sun since the afternoon sun is quite intense. i hope this helps.

6 hours of sunlight is supposed to be full sun, so the things that are getting morning sun and shade in the afternoon probably count as full sun. Many plants prefer to get sun in the morning and shade in the heat of the afternoon, especially in hotter zones. I would venture to guess that a lot of "full sun" plants will need a little shelter in your climate.

I have a dilemma similar to yours; I don't have time to sit and figure out where there's sun and where there isn't, so this is what I've been doing. When you buy your plants, leave them in their pots in the place where you want to put them for a couple of weeks. If they don't turn yellow, they're probably getting enough sun to live. They may not get enough to bloom properly, but the vast majority of plants don't mind being moved once in a while, so you can always fix that later.

Of course, I'm the kind of gardener who buys things when they're on sale and plops them wherever I think they'll look good, so if you're a planner this might not be the technique for you. Just remember that gardening is an art, not a science. :)

Tara