I don't want to rain on anyone's parade but I have fished in lower Chile
and Argentina 4 times over the last 10 years. I think you are, on the
basis of my experience, going to run into access problems on most rivers
unless you work to some extent with the outfitters.

I had good to excellent fishing on all the trips. If I am fortunate to go
back to the area I will most assuredly at least contact some outfitters.

Good luck and let us know how you do.

Jack in Brentwood, TN.