My friends and I are looking at a 3 week trip to South America too. We like the cost and itinerary on the Uniworld cruise, which leaves from Santiago, Chile, sails around the horn and ends in Buenos Aires. Patagonia, Falkland Islands and Terra del Fuego are included. Haven't heard any firsthand reports, but you might check out the website to see what they offer.

where can i go in the summer in South/Central America but so that its still summer and not winter
?