It depends on the elevation, weather, your aclimatization, and comparison between nighttime and daytime temps. The highest you list, Bryce, can be cold enough to make you wish for a jacket when you first wake. When skies are clear I'm betting that it gets down into the low 40's, even high 30's at night. Escalante is not so high, but you'll still relish a sleeping bag. Page on the other hand only feels cold at night in contrast to the high daytime temps. I've slept out in the vicinity with nothing more than a light blanket. I don't enjoy heat, so in fact I turn into a night owl in such locations simply because the nights are in the 70-s and 80's rather than the 90's and 100's like the days.
We carry old cotton bat type sleeping bags in summer (30 degree rating as I recall), zipping them overnight in the high country, leaving them unzipped at elevations like Escalante, and simply using them for padding beneath us while covering with a light blanket or even a sheet in the hot regions.
Does this help?