Hi Ceci, I recommend you to go to: Recoleta all saturday long (it's really nice); Feria de Mataderos (on sunday morning, lot of tipical argentinian stuff); San Telmo and see a lot of stuff about tango (on sundays evening there's a market and they dance on the street); and museums are free on quarta.
Then, about going out... there's always a place to go...
Write down my e-mail...
nsblauzwirn at gmail dot com
However, I work in another hostel (St. Nicholas)
Don't believe in ranking really...
cheers
Nick