Are you referring to public or private pre-schools in SF? For public, the school system gives the low income residents the priority first. For private, you should start putting your daughter's name on waiting list at least one year before she attends pre-school. The below website should give some great info about which school you want your daughter to attend.

http://www.greatschools.net

Good luck!

My brother's son also about the same age, and due to the fact he bought a tiny 1br in San Francisco recently with about $650,000, he does not have much extra to spent on preschool of his son. He said he plan to pay off the mortgage in a few years.

Well, I told him the best preschool is "home" and the best preschool teacher is a "retired Chinese professor or teacher" immigrated to the US. So, he hired this ex professor of Peijing University to babysit his son. I can almost guarantee you that his son will out peform every kid at that age, and eventually get into top university like Berkeley.

Of course, if you can get a retired Harvard University professor willing to babysit your daughter, it should work too.

I highly recommend joining the Golden Gate Mothers Group. http://www.ggmg.org/ We have posted questions like this or searched the archives on GGMC and gotten literally dozens of responses. Several mothers have done systematic visits and assessments of all the top schools and posted their findings. It's the Trulia Voices equivalent of an online community where mothers are the experts. Good luck!