Housing in SF itself has not changed much in the past year. To buy a place, prices are down maybe 5-10% in the city. Outside the city, housing prices have been dropping like a stone. Rentals had been going up for a while but look like they're stabilizing and maybe dropping from what I've seen.
Inside the city your options for public transport are basically limited to bus or light rail. If you live outside the city you may be able to take either BART or Caltrain in to the city.
It is a multicultural city, although there are pockets of individual nationalities that vary by the neighborhood.
Crime is always a sticking point. There are a few sections of the city that have seen crime go up recently. SF has the crime maps online though, so you can check out how safe a particular area is yourself (
Sfgov.org | San Francisco Police Department: SFPD CrimeMAPS).
I don't have kids, so I couldn't tell you what the schools are like personally. From what I've heard, there are a couple decent public schools, but on the whole they're pretty terrible. Private school options are all over the city depending on the age of your kids.