If you want to feel safe, you may not want to use the CrimeMap service provided by San Francisco's SFGov.org. You can enter any address or cross streets, a time frame, and the types of crimes you want to know about, and see what's been reported. What's scary is that there appears to be as much crime on the best, cleanest, most expensive, and safest "feeling" blocks as in an area that you might otherwise think isn't a safe area.
Like avoiding watching the movie "Jaws" before swimming in the ocean, I'd avoid use of the CrimeMap service if you don't want to get freaked out about San Francisco. Personally I think there could be some explanation for how the actual crime goes against the "feel" of an area. And that's that this is "reported" crime... so maybe there's more reporting going on in some neighborhoods???? But... if you want to dive in... here's the site:
San Francisco CrimeMap