I want to open a small bakery in san francisco and need to know which
neighborhoods in the city spend most on gourmet foods. Any statistics
on demographic spending on high-end bakeries or other food services
specialty shops is what I'm looking for.

This doesn't answer your question about San Francisco demographics but
will give you a good idea of where the bakeries are. You can either go
where there seems to be a recognized audience where there are several
bakeries already or you can pick an area that seems under served. Good
luck.

http://sanfrancisco.zami.com/Bakeries
http://www.sallys-place.com/travel/san_francisco/ps_bakeries.htm
http://www.sfstation.com/classification.php?key=FSB
http://sanfrancisco.areaconnect.com/restaurants/bakeries.htm