In reply to MikeR:
I'm from argentina and climbed a few times in el Chalten and Bariloche.
Bariloche is easy, mostly sport climbing, there is a guide, and you can find partners relatively easy.
Chalten you've got a sport climbing guide and there is a new guide for the fitz roy and adjacent peaks which is amazing. I'm not sure about hiring a guide to join you, but as you said... you need to be careful. Is definitely not like a climbing day at Pembroke.
Another thing is... that area is super turistic... so expect prices to be very expensive, even more than what you would spend here in the UK or Europe.
If you want to buy the guides just let me know, I can help you find them.
Juan