To get a real feel for the Tango culture in Buenos Aires then you must go to a Milonga (Tango club). As I walked into Sueno Porteno Milonga I felt as if I had walked back into a cheesy disco in the 70's. But instead of the BeeGees, the speakers blared tango music.
You can grab a table near the dance floor and simply watch the locals practice their best moves or if you are versed in the tango then you may want to participate. It won't take long until you get asked to dance if you make eye contact with someone.
There was diversity of fashion from casual to formal tango dresses, and a diversity in age ranging from 30 to 80 years old! This is the real deal - tango not for tourists.
Details: Sueno Porteno MIlonga is located at Av. San Juan 3330 in Buenos Aires. Don't show up before 11PM else you will be disappointed as everyone normally comes around midnight. There is a small cover charge to pay at the door. Photos are generally allowed as long as you aren't a nuisance.
Sueno Porteno Blog/Website - in Spanish - http://clubdetango.blogia.com/