Sunday night in San Telmo you get great deals on Tango.
I went to one with a meal and as much good wine as you wanted. It was Michael something or other. I will post when I remember.
A football game is essential. If you are not confident enough to go yourself there will no doubt be a hostel trip.
If you go to Tortoni go early to avoid dissappointment.
San Telmo is a fantastic base.
I wasn't keen on the botanical gardens (and cats) myself but in Edinburgh I think I am spoiled with about the best I have ever seen. The zoo is ok but the one in Cordoba, for example, is way better. Not enough room for animals here imho.
Depending on how serious you are about religion there is a religious theme park near the airport. I found it highly amusing.
Clubbing and bar hoping is of course fantastic at times. Be careful with drunken bearings though!! Taxi it in fact.
Are all the tango shows at Plaza Dorrego in San Telmo? I am staying in San Telmo for my first weekend in Buenos Aires. I am definitely hoping to go for a football game.
Thanks for the tip on riding the taxi back from any club/bar-hopping expedition.