I have been following the CR Forums for some time. This post finally prompted me to register. First, FSU_Dan, wishing you a safe and speedy return from Afghanistan! Second, I hope you do not mind piggybacking on your post.
I am also planning a trip to the Grand Canyon, Monument Valley, Bryce Canyon, etc. in May. I will be shooting with a 7D and have an EF-S 15-85 and EF 70-300L. My only real expertise (a stretch) is motorsports (thus the 7D). I am wondering if I will be happy with the 15-85, or if I need wider (say the ef-s 10-22) or faster (a prime)? I would appreciate feedback from landscape and canyon shooters regarding lenses for the 7D on this trip.
Also, I have a good quality circular polarizer. While I hope to be able to shoot early and late, I do not plan to put the camera away mid-day. Will a neutral density filter be a must?
The 15-85mm will be fine for the Grand Canyon. I took along the Tokina 11-16, but I don't know if I even used it. I think I took more shots at the 85mm end than I did at the 15mm end. (Crop shots of the rising and setting sun playing against canyon walls and rocks that jut up from the bottom of the canyon).