I've found it to be about as bad as conservative media makes it out to be. It really depends where you are, but I've seen people smoking crack (I assume, maybe meth), and I've seen people shooting up in plain view in daylight. There are exposed needles and human feces on the ground, and you will absolutely notice it if you walk anywhere. Boots are for sure recommended.

I know that stuff happens everywhere, but it's so far out in the open in SF, you can't avoid it.

Part of it also has to do with the topology of the city. Homeless people don't want to live on hills, but rich people do, so that creates pools of homeless camps in flat areas.