Gualeguaychu! or, Argentina's answer to Carnival.
If you don't want to be stampeded to death, or you don't want to pay lavish amounts of money just to sit at the back of a football stadium to watch the carnival parade then go to Gualeguaychu instead. One girl who had gone to carnival in Rio that year as well said this one was better because you could actually see what was going on.
Gualeguay is about a two hour bus ride north of Buenos Aires on the rio de la plata, close to one of the border crossings with Uruguay. Carnival there consists of massive beach parties, by far the highlight for our group, and then later every night the carnival parade at the fair grounds.
I have never been to the real deal in Brazil, but I don't really see how anything could be more lavish. All of the floats were at least 20 feet high and resembled floating palaces. Our close proximity to them increased the experience because we were able to appreciate the detail, and not just the overall shape as we would have been able to if we were much farther away.