Shade Tree Recommendation

I wouldn't go with a fast growing tree. Neil Sperry, garden guru, talked about this on his show. I rarely listen to it but just happened to have it on in the car recently. Anyway, he said it is smarter to plant a slower growing tree because the fast growing kind are not very hardy, are more suseptable to disease, and don't live very long. I would ask someone at a good nursery or tree farm, not Lowes and Home Depot. It is hit and miss at those stores whether or not the person you speak with actually knows what they are talking about.

Fruitless Mulberry trees grow fast and give good shade. I would avoid the weeping willows mentioned by some others. They are beautiful trees and frankly I would love to have one myself, but they have a bad tendency for the roots to grow into your water pipes. Best leave those to the riverbanks.
I would put in a fruitless mulberry for some quick shade, and if you have the space, also put in a fruit tree of some sort to grow up slowly and take over later. If there isn't space for both trees once full grown, you'd always be able to take out the fruitless mulberry once the fruit tree is big enough for shade.

We have a weeping willow on the SW corner of our lot. Low maintenance, and we are a zone 9, which I'm sure you are as well. I've always wanted a tulip tree (a relative of the magnolia with the most beautiful blooms you've ever seen - but it does drop its leaves every fall). You might try a maple tree? There are a few varieties than do well in California.

The links below are per a Google Search for "fast growing shade trees for California."
http://www.fast-growing-trees.com/ShadeTrees.htm
http://www.hotgardens.net/fast_growing_trees.htm
http://forums.gardenweb.com/forums/load/calif/msg07194852...

Also as a reference:
http://www.cal-ipc.org/landscaping/dpp/plantpage.php?regi...

The problem with fast growing trees is they tend to throw a lot of junk. Weeping Willows throw tons of branches. I have one, love picking them up. :( Another is Sugar Maples, tons of those helicopter things and you end up with trees growing everywhere.

The best I can come up with is White Pines but even they shed needles and pine cones.

I know it is not what you want to hear but you may want to have patience and go with a slower growing tree. We have to replace three because of the storms. I am thinking of a Magnolia but haven't figured out the other two.

Talk to you local nursery. I am a big fan of fruit trees - our last house had a beautiful cherry tree that gave shade, pretty flowers and fruit. I personally would stay away from conifers, even though they are "evergreen", that really means they shed needles yearround - at least with deciduous trees you're only dealing with leaves once a year!
Good luck!

Globe Willow (not a weeping willow) is a very fast growing tree and is awesome to watch and listen too - it looks like a womping tree when it is really windy (Harry Potter reference). Texas Ash (not sure about how it would be in CA) is an awesome shade tree and grows very fast. Neither of these trees 'throw a lot of junk', in fact they throw no junk at all. Bradford Pears grow fast but I don't think of them as shade trees since they grow in such a tight ball.

We moved on a lot w/ no trees at all. We planted 20+ trees (oaks, maples, pecans, elms and a Chinese Tallow) and the globe willow and Texas Ash are by far the largest trees and have grown in the shortest amount of time.

Those are what I have experience with. Good luck!