I did this program during the World Cup this past summer:
www.ecela.com
Went to
Chile: Santiago
Argentina: Buenos Aires
Peru: Lima, Cusco
Over a period of six weeks. I didn't do medical spanish, although its offered in Santiago and I in fact met a second year there who was getting 1 month 4th year elective credit for learning it and shadowing at a clinic. I also met a lot of Koreans from Samsung and this other telecom company who'd been sent there to learn it for a year.
I went from knowing absolutely no Spanish at all to being able to participate in short, informal conversations with people. I think the biggest benefit, aside from traveling around, was tuning my ear up to hearing the actual language spoken by native speakers.
I wish I could've stayed longer. I was so depressed when I had to come back to start second year. Anyway it's been four months and while my speaking has deteriorated a bit since I don't ever do it anymore, there are a lot of spanish speakers in clinic and it's pretty awesome to at least understand what they're talking about.
I will absolutely be going back my fourth year. It's one of the best things I've ever done.