I think it's unlikely, since most of the cruises down there aren't part of the major cruise lines IIRC. Even if it was possible, it would almost certainly be a massive amount of points.

That said, I did a trip there my senior year of college, and it's an absolute highlight of my life. Simply extraordinary.

ETA: I seem to recall hearing the you could often find last minute prices that were much lower, if you were willing to go on like 2 weeks notice.