I want to plant a tree on my property. Where can I find information about what varieties of tree should I plant here in San Diego?

First decide what tree features you want:
www.treesaregood.com/ has a good discussion of how to identify your needs:
"Considering that most trees have the potential to outlive the people who plant them, the impact of this decision is one that can influence a lifetime. Match the tree to the site, and both lives will benefit."

Now use this search tool to help you identify the exact tree that meets your needs:
http://www.ufei.org/  to get to the database of 1481 trees with 49 attributes. This is the grand-daddy of tree search engines; it's from Cal Poly SLO.

For a second but smaller opinion, also check:
http://bss.lacity.org/UrbanForestryDivision/StreetTreeSelectionGuide.htm   which gives you a search of a 150-tree database useful in Los Angeles and of course San Diego.

Next, if this is going to be a street tree, i.e., in your parking strip, check to see if the City of San Diego shows your choice as an "acceptable" street tree:
http://www.sandiego.gov/street-div/urbanforestry.shtml and click on Tree Selection Guide to find the street trees acceptable for City of San Diego residents. If you don't like any of these, you may request approval from the Street Tree Division, but these are the trees approved for use curbside in San Diego.

If you already have a tree and want to know what kind it is:
http://www.arborday.org/trees/TreeID.cfm to use an automated tree ID program which asks you questions and narrows down the identity of your tree. This does not have all trees growing in the west, but it contains many common ones.

And finally, some free stuff:
At http://www.arborday.org/shopping/memberships/memberships.cfm?membership=trees
Arbor Day Foundation gives away 10 free trees with levels of membership (some would even grow in our climate zone).

The Southern California Center for Sustainable Energy ( https://energycenter.org/  ) gave away 33,500 trees through two programs, it's South Bay Shade Tree Program and it's Cool Communities Shade Tree Program. The last of these finished in 2008 but we can expect more give-away's in the future. When the numbers were tallied, the positive effects of these trees far exceeded the carbon required to fund the programs and run the business.

These 6 links will help you find the tree that is just right for your needs.