In the Sonora I might take a bit more precaution, but on the high Colorado Plateau (Cedar Mesa area you're talking about is mostly 5500-8000' iirc) I wouldn't worry too much. Do check the weather, but I've camped on the canyon floors many times. I was in Dark Canyon in November and there must have been a crazy huge flash flood at some point last summer. Lots of pretty good sized Cottonwoods recently knocked down and debris really high on trunks/branches.