Stay outta trouble, learn running, figure out various tricks - kick cars so alarms go off, maybe carry mace and some shrieking device, look crazy when threatened, I don't know, hiss real loud, that'll freak people out, they don't know maybe you're mentally retarded and basically a bigger chimpanzee. They'd never mess with a smaller brained ape your size, an ape half your size can totally mess people up - an ape will bite off fingers, gouge out eyes, rip off ears... without any martial arts. Don't look like you're clever enough to figure out that if you fight back you're more likely to die. Looking clever is stupid anyway.

My parents made a mistake of being in Russian part of Soviet Union when Soviet Union broke down - can't really blame them for not wanting to be in a hostile-ish-to-russians region near border when a military superpower goes down, though. The crime rate was like you wouldn't believe.

Most martial arts schools I've checked out have monthly tuitions in the $50-150 range; so on the low end, that's at least $600 tuition. You won't get much benefit out of just 1 class a week, but 2 classes a week at an hour & half a piece (travel, changing, recovery + 1hr class ) times 3 weeks a month times minimum wage is $72 a month or $864 a year. So paying for and going to the classes is going to cost you >$1500 a year. That could be a large chunk of what it takes to get out of poverty, for example, that alone is a good chunk of many community college tuitions.

Combine that with the low absolute rate of crimes and the unknown effectiveness of standard martial arts for dealing with said crimes...

being poor doesn't mean you have to spend time around other poor people. It's certainly more difficult, but it's worth it. In addition to personal danger, your habits and behaviors tend towards being the average of those you surround yourself with.