Well since you seem interested:
I am a permaculture designer and teacher in SF, whats permaculture? well this page is so-so at describing it:
http://en.wikipedia.org/wiki/Permaculture Theres lots more on the web if you care to dig, or not dig as the case may be
(you will get the joke if you know more about our gardening style)
Heres a video of a garden I created in San Francisco:
http://www.youtube.com/watch?feature=fvwrel&NR=1&v=VaUNBsO9zgIThis garden has gone from vacant lot to forest of food in just under 4 years. I have over 75 fruit and nut trees alone, not counting all the perennial shrubs and so forth. BTW, thats not me in the video, I have never actually met that dude and I am not sure why he was there. At any rate it shows what we have done fairly well, if a bit inaccurate at times.
I also started this project, about 1.5 years after that garden above:
http://www.hayesvalleyfarm.com/I led this project for the first year, implementing the initial systems and teaching folks ow to do it all, then I went back to my humble little garden with all the fruit trees.
So anyway, I have a bit of a reputation around here for the stuff. Folks seek me out when they want to have productive landscaping in their homes or in their parks. I do a mix of public and private work and I honestly find it easy to get 100 trees in every year.
For trees in the urban setting, I advocate for bush style pruning which keeps them small therefore allowing more trees of more variety meaning more high quality fruit throughout the year instead of bumper crops of one fruit all at the same time, which you get from big trees. see:
http://www.utahhort.org/talks/2002/LynnLTS.pdf10 trees in a single backyard is easy, i often do much more. I also like making fences out of live trees, imagine a fence that grows stronger with age and flowers and gives a variety of fruit! You can do some neat stuff with living trees:
http://thoughtsonarchitecture.com/2009/09/08/botany-building/