I second the Palermo Dist. The district is pretty central to social-type things like nightlife, cafes and shopping. The subway works great in BA and the cabs are pretty cheap by SF standards. Lots of great restaurants in that area, great bakeries, the big grocery stores will deliver your groceries for free.

I would say one of the only downsides to BA including Palermo is all the dog crap on the sidewalks. Palermo is not that well lit at night and the BA residents notoriously don't pick up after their dogs. Lotsa people live in big apartment buildings with no backyards, thus they let their dogs out the front door to crap on the sidewalks. You'll see when you get there. Just watch your step when walking and drunk at night :-)

Here's my last tip: many of the Tahoe ski resorts employ students from Argentina, Chile and Brazil to work the ski season. I just gave a couple of nice BA students that were hitchhiking on hwy 50 a ride to Kirkwood last week. If you are a skier or boarder, head up to Tahoe and make some friends. Argentinians on the whole are super friendly!