I am trying to decide whether to focus on Monument Valley/Canyon de Chelly area or go to Arches/Canyonlands area.
Arches/Canyonlands offers more choices and variety Substantial elevation differences allow you to choose what temperature you want at what time of day. You could spend weeks here and not scratch the surface. MV, less so. C de C is nice, but both are much smaller and offer less choices than the Moab area.
Then there are the must-have guide issues at MV and Canyon de Chelly. I prefer to work alone.
Is one of these areas likely to be too hot or windy at this time of year?
Winds can arrive any time of the year. Hot? Not yet, but soon. Should be wonderfully green in Canyonlands about now.
Don't forget Dead Horse Point State Park, a half hour north of Moab. Sunset or sunrise. Better than the Grand Canyon, IMHO.
Good shooting!
Peter