Spirit Airlines is an American ultra low cost carrier operating routes throughout the United States, Caribbean, and Latin America. They currently offer flights from Miami/Fort Lauderdale, Florida to Bogota and Cartagena, and will begin offering direct daily service to Medellin on March 1, 2009.
To get a sense of the fares, I looked up a one-way, non-refundable flight from Fort Lauderdale to Medellin. A regular seat, at the regular price (including taxes), costs $175. If you join the $9 Fare Club, then for $39 per year, you receive $9 off each flight you book, which could offer long term savings for frequent fliers. The flight time is 2 hours and 20 minutes. I was unable to find an available March flight from Medellin to Fort Lauderdale.
A round trip flight from Reagan National Airport in Washington, DC to Medellin in April runs $438 and includes one stop over in Miami each way.
A round trip flight from LaGuardia Airport in New York City to Medellin in April runs $540 and includes one stop over in Miami each way.
Great savings for beautiful destination!