I've lived in three different neighborhoods of the city, and none of them have problems with human feces, and that's to say nothing of the outer neighborhoods that are mainly single family homes.

This is, in fact, one of the reasons that SF's very real problems persist year after year. The people with resources are largely insulated from it's problems. California's major cities are a lot like Latin America in that regard. It's great to be upper middle class or higher, since almost all the troubles are kept largely out of sight.