You can fly Lan or Aerolineas Argentinas, with their surcharge for foreigners or take the bus, maybe stop in Bariloche or Puerto Madryn along the way.
I saw a penguin walk up on a beach just south of Mar del Plata a few years ago. I think it was out of it's range, it looked tired and weak, and maybe a little ill. Some people "rescued" it and were going to take it to a vet. But it was an interesting sight to see. They certainly have a range far north of Ushuaia, you don't need to go all the way there to see one.