You WILL be waiting 15 years for any tree to make a significant pool of shade - especially if it is not going to be planted right where you sit, as in the same place you would put a patio umbrella. So you probably need to be thinking about an architectural solution instead, such as a gazebo, lath house, trellis and/or patio umbrella.

California has its own variety of redbud tree. That might be a good choice. If not the Texas Redbud or standard Eastern Redbud are possibilities.
Mexican Plum has worked well for me as a small tree that grows somewhat fast and puts out nice shade.
Desert Willow is a flowering tree that can also be a bush. Keep it pruned to a single trunk. Puts out pink flowers from early summer to fall.

You will probably want an evergreen tree, so that you will have shade all year.

Consider our native Heteromeles arbutifolia. It is a large shrub that can be trained into a small tree. It grows quickly, also

My choice would be a jacaranda. The Golden Rain is very invasive.
Consider also Madrone Arbutus menziesii
Strawberry tree Arbutus unedo
One of the Bottlebrush species Callistemon would be good
Royal Poinciana Delonix regia
There are several small to intermediate Eucalyptus trees.
You should visit a good nursery in your area. Not a Lowes or Home Depot. The nursery would have a larger variety and a knowledgeable staff with ideas you might not have ever though of.

thanks to all you who have posted your recommendations. I am looking at all of the wonderful trees you mentioned and hopefully choose one this week. I have gone to nurseries and spoken to landscapers who all have very different ideas so choosing something fairly permanent is a bit intimidating.
thanks again!
Ally