Hello!,
I went on this holiday last March and it was wonderful! Utah was brilliant (the cookout was hilarious) Bryce Canyon, Sedona, absolutely breathtaking. You'll need warmer clothes (layers) in Utah in March - some of us had to buyfleeces) as there was snow on the ground, but obviously warmer as we came further south.
Very hot in Vegas and Scottsdale. I was fortunate to have the four nights add-on at the ranch in Tucson which was a wonderful experience but they don't seem to do that anymore. The whole holiday was unforgettable!
I think we did the holiday in reverse - we started in Vegas.
Enjoy!
Pat