Just about every day, I hear from my porteña housemate about new rape and assault cases happening in these areas. I've even seen pictures of the suspected "violador serial" taped on people's doors. So, from what I understand, women should be especially careful what with this dangerous suspect on the loose.
So, if some strange man approaches you at the front door of your building and pretends that he lives there too, or says he lost his keys, don't let him in. And if there is some unfamiliar person in the elevator, don't get in. My experience is that sometimes, I see a shady person lurking near my building, and in that case, I just walk around the block or find some place to go. These shady guys don't stick around too long.
So, if some strange man approaches you at the front door of your building and pretends that he lives there too, or says he lost his keys, don't let him in. And if there is some unfamiliar person in the elevator, don't get in. My experience is that sometimes, I see a shady person lurking near my building, and in that case, I just walk around the block or find some place to go. These shady guys don't stick around too long.