I've been robbed on the street twice in SF, once in 1970, once c. 1984, both times within a couple of blocks of Haight and Fillmore, which once had the distinction of being the most dangerous intersection in the city, before a particular bar closed, and 16th and Mission became the new placeholder. In one case, I gave way "gracefully"; in the other I was checked out, tested, distracted (not given an opportunity to be "graceful"), jumped from behind, and hurt (glasses broken, black eye, and it could have been much worse).

The principal thing I learned was: don't be drawn into an interaction, because that's the whole process: to socialize, get you to stop, pause, and fix yourself as a target, and then to test your limits and reactions by crowding your space. In fact taking your sunglasses probably wasn't the target but the test, which ended when you finally acted appropriately by objecting and leaving. Test for what? To intimidate you into buying drugs, which you refused, or even someone to target in the future (though I hate to consider the possibility).

Part of what trapped both of us were the social conventions and misplaced liberalism that tell us to act civilly and with a certain openness, emotional genuineness, and assumption of goodwill to everyone we encounter. This only works in some places, if ever: certain small or closed communities, college campuses, working environments: places where an assumption of absence of predators isn't quickly punished.

A secondary, minor thing I learned was not to be fixed in space or intention, i.e. keep moving, and have alternate available routes always available (fluid-ambiguous). I was trapped at a deserted bus stop at midnight where I shouldn't have been, near the projects, having had two or three drinks. Asking to crash or calling a cab were the safe options. Walking out, say to Geary ~a mile to a bus stop with a more predictable or limited risk, wouldn't have been risk free but probably a lot safer.

In my experience, yes, unsafe or sketchy neighborhoods tend to be cheaper, but not that much. With some scouring the ads, you can probably find a share rental or an inlaw apt. that isn't much more expensive, is safe, and probably quieter. It might entail a less central location, longer travel times, a less vibrant neighborhood, and maybe roommates that you don't now have to deal with, but it's all likely worth it, or even necessary, depending on who you are (age, gender, size & strength all have something to do with your candidacy as victim, which you don't need to feel apologetic for).