I too have heard of tourists who think they are cool by taking a bus to the airport (Ezeiza) and then got robbed. No Porteño would take a bus to an airport. If you can afford an air ticket, you can afford a taxi. If you get on a public bus with suitcases, looking foreign by the way you dress, look and act, you are asking for trouble. BA is not New York where anyone, regardless of nationality, can hop on a bus or a subway and reasonably blend in.