http://news.msn.com/staging/world-cup-over-but-some-argentines-wont-go-home
Argentines don't need a visa, or even a passport, to visit Brazil. A government ID card will do.
Mello spoke at the Sambadrome, which was turned into a makeshift campsite to help accommodate the waves of Argentines who arrived by car, bus and motorhome during the World Cup. The site was closed last week, and the last campers were evicted. Media reports said Argentine consular officials were there to help organize return transportation for people whose money ran out or whose documents were lost or stolen, but many reportedly weren't interested in such help.