IF you are going to talk in a loud voice everywhere you go, IF you are going to walk around on your own at night in the center, drunk, IF you are going to carry everything you own from stashes of cash to ipods to Nikon D3's, IF you are going to wear obviously touristy/hostel-type clothing and IF you are going to go wandering on your own into the villa then yes, you probably will get a gun pulled on you by a crazy crack addict. I am a foreigner and I can spot a tourist a mile off, especially an American or a German (with my random radar that I have). Generally speaking, being low-key helps. A lot.
Buenos Aires is an amazing city and so don't be afraid to go!