Having lived in SF for about a year now, it's actually quite a clean, beautiful, and safe city IF you just stay away from a big chunk of the center. My wife and I pretty much try to avoid it at all costs now, which is sad because there's a lot of good stuff there (architecture, theatre, restaurants, the tech scene, public transit arteries, etc.) but there are also plenty of interesting and beautiful neighborhoods to explore that don't have any of these problems, so we still enjoy living here a lot for the most part. It's a utopia and dystopia all wrapped up into one.