Noe valley and Richmond have homeless people. In the Richmond, on geary you'll see a lot of homelessness and drugs, especially from 4th-10th. There are also a few near Safeway on cabrillo. In noe you'd definitely see it on 12th Street. I've seen some really unstable people clear out coffee shops because they we were ranting in the middle of the shop.
There aren't many homeless people in the purely residential areas, but they are definitely where the businesses are.
12th St isn't even close to being in Noe. There's usually two homeless people in Noe, one woman who always sleeps between Church and Noe on 24th St, and an older man. Outside of the misfortune of being homeless, they don't really cause any troubles, and most people in the neighborhood often give them food or a warm tea / coffee. There's not much we can do on our own, and the city doesn't really seem to help sadly.
The reality of the matter is that SF is the diametric opposite of NYC. In NYC, people live in Murray Hill for a year, move somewhere else and talk about their amazing experience in the UES for the rest of their lives.
In SF, they live in new builds (all of which are in former non-neighborhoods that were either highway overpasses or industrial districts), move somewhere else and talk about how they basically lived in Pac Heights and even there it's scary.
Sorry, you're right. I actually meant to write 24th street. Also, I do not blame homeless people for their situation. They are not getting the help that the state and city needs to provide, but aren't actually interested in providing.
There aren't many homeless people in the purely residential areas, but they are definitely where the businesses are.