About the convention, an Argentina woman told me that. She said they actually have conventions, come in suits and ties. They're professionals. So don't let clothing fool you. Some of these guys dress up like businessmen, eat in restaurants and steal your computer from under your chair. One man I talked with met a friend in a restaurant, two men sat behind him in business attire and had brief cases. Now would you suspect them? He didn't. The place was pretty empty except for those two well-dressed men. He put his briefcase with his computer between his feet on the floor. When he got ready to leave and picked up his briefcase, it had been switched. You have to keep things in your lap. And yes, it is hard to stay perpetually alert. He said that, after the fact, he should have wondered why, with so far people in the place, these two guys sat right next to them. Usually people will opt for more space if it is available.
For newcomers, we learn here to keep important things in different locations. I have some rather creative locations, but as with investments, diversification counts. Keys one place, ID another place, serious money another place (I've been told leave some bills in your purse just in case you do get robbed). I carry my purse actually, almost as decoy. Also I only carry about as much money as I will need where I am going.
All that, and I still nearly got robbed by this sweet lady who appeared to be defending me against this rude, inconsiderate man trying to deprive me of a place to hold onto. And yes, the subway was packed.