UPDATE: This deal is dead.
Jet Blue is having a sale on their new route from Fort Lauderdale to Lima, Peru from only $139 each way ($302 roundtrip all-in). Their new route starts November 21, 2013 and these prices are available through December 31, 2013.
You can add on a roundtrip to Buenos Aires from Lima for $415 and get a complete roundtrip from Miami to Buenos Aires for about $717. Not a bad deal…
UPDATE: American Airlines is also running a fare sale to Latin America, but unfortunately not to Buenos Aires. You can however fly coach from New York or Miami to Montevideo from $931 and (even better) business class from only $1949. Tickets must be purchased by May 8, 2013 for travel between May 15 and June 6, 2013.