because it makes a difference here in the People's Republic of Kalifornia.
I would call or email Frank Pisciotta @
www.cyberfly.com. He goes to the Coyhaique area of Chilean Patagonia to a lodge, and he could tell you what to bring that would best suit the area. I know you said you were backpacking so weight is a premium, BUT a once in a lifetime trip, it would be a shame to twist an ankle while wading in a river, or get your foot bruised by a rock.
If it was me, I would be leaning toward sturdier boots with good ankle and insole support, and good toe protection. I love my Simms Guide boots, but they weigh a ton. (Bring extra laces and extra patch kits for waders)
I envy you! YOU SUCK!!!