Hey!
I was born in Buenos Aires but have been living abroad for a year and a half, so just came back home! I would suggest you to go to some bar or pub, I love Tazz (
http://www.tazzbars.com/) but there are a lot of good ones. You should hang out in Plaza Serrano, there are nice restaurants also. And you can't miss going out in Puerto Madero.
Buena suerte!