On our hike (yes it took us two days to hike the 20 miles! LOL!) I used a Big Agnes 15*F, wore a light fleece top, a cap, and medium weight smartwool leggings, and socks and was pretty comfortable. I sleep VERY cold. My hiking partner used a sleeping bag rated 35*F. She didn't wear much in the way of sleeping clothes as I understand, and she was also comfortable; she doesn't sleep as cold as I do. When I woke up I checked the temp and it was about 52*F. I have no idea how it will be in the upper elevations, but by the time you get there it should be warming up considerably.
I'm one of those hikers that likes comfort, so I tend to over carry so I'm not cold at all at night. Oh, and I didn't even use my sleeping bag in the proper manner for optimal warmth (close around the neck, hood up). I did use a sleeping pad and so did my hiking partner (I used an inertia x frame, she used an Ether Thermo6). We both used tents.
I hope some of this information helps!