I was going to shoot Yosemite as a gear check for cold weather shooting prior to a fall trip to Patagonia, which you mentioned you were thinking of going to!
I didn't make it to Yosemite, one of my concerns was the cold weather :-) no really so many photographers shoot the area, but It is definitely on my bucket list.
I did make it to Patagonia, in April of this year and I have to tell you; it is one of the most target rich photographic environments I have every been in! If you go you will love it!
I went to Fitz Roy Valley for fall colors, April 7th to the 17th, missed peak colors by a few days I think as I watched the valley just get better and better. bring wide, macro and telephoto as there are endless things to shoot even when the light is poor, which for me was about 70 percent of the time.
If you have never been you will freaking love it! I'm re-scheduling a Kenya trip so I can go back again in April!