South America 1.5 week(s) away... yah!

I've been so busy with fashion week that I haven't gotten a chance to talk about my trip. I'm going to South America (Chile, Peru and Argentina) for 3 weeks leaving next Saturday and I'm super excited! I will be backpacking with 2 other friends, staying in hostels and living on the cheap while trying to do and see as much as possible. The only things we really have planned are Machu Picchu, Iguazu Falls and we really want to go to a soccer game in Argentina. Any other ideas, advice etc?