Visa requirements

Would you need to have a Visa to get to Argentina?
Look for that info in this webpage http://www.consuladoargentino-losangeles.org/
In 2010 Argentina started to ask for a 'tasa de reciprocidad' fee of reciprocity to citizens from USA, Canada and Australia.This is not a Visa.
IIf you are planning to visit Iguazu Falls it is also worth looking at them from brazilian side. Maybe you will need a visa for Brazil. American and Australian citizens do need one.
You can get it in Buenos Aires, but I suggest that you get your visa in your own country before coming or you might waste time trying to get it. You have to fill out a form, then go to a bank for the payment, and then wait three week days. It was three days in March 2006. This may change.
Be aware that you won't have your passport until they give your visa.

You need to go to the Brazilian Consulate, not the embassy, to apply for a visa. Make sure you have all your information about your plane flight in and out, where you're staying, and a contact person's info to be able to fill out the form completely. If you don't have all the information for the form they'll send you away until you have it all. More info in Brazilian Consulate in BA http://www.conbrasil.org.ar/ Look for "If you need a tourist Visa for Brasil"