Hi,
I spent three weeks in the area last september and did a writeup which you can find here:
https://mattbrisbin.wordpress.com/
As far as water goes no treatment is needed. Strange right? I took a sawyer and tablets and ended up leaving them at the hostel while I was out as no one treats the water. I have to say, to this date, it's the best water I've ever drank. At first I was quite paranoid since I've never drank straight from the river/stream/source but I never had issues.
Feel free to PM me if you have any questions. Highlights of the trip where TDP, King penguins, Perito Moreno glacier and the biking out to the milidon caves.
Had a blast down there. Have fun and good luck planning!