Buenos Aires is an awesome city with a bajillion things to do, and the CEA staff was always helpful in recommending activities and helping us check off our list of things we wanted to do. My classes were all liberal arts classes since that was my program, and they all had an immersion component, where we'd go on field trips and link the things we were learning about in class to the country we were living in.
Everyone coming to Buenos Aires should definitely go see a fútbol game, because the fans in Argentina are so incredibly passionate. You should also go to a Milonga, a tango club. The one downside of my semester is that I didn't get to travel as much as I wanted because Argentina is so huge that a lot of the places I wanted to go couldn't be visited in a weekend because the actual commute took an entire day each way.