Hi RayZ59,
I've just been to Utah once...was traveling from Grand Junction Colorado to the Grand Canyon..
went north to south ...by way of Moab, Mexican Hat, Monument Valley...
Great scenery...but don't know if it would be convienient for you if you were coming from Las Vegas.
It was in Feb. last year...weather was great...got into a dust storm north of Monument Valley....but I think that must be pretty common in that area.
Coming in to Monument Valley from the north....I just had to have my wife take a picture in this one spot...it turns out EVERYBODY must think the same thing...
"Forrest Gump Hill" 

http://mstecker.com/pages/mvapproachroad.htm

http://www.youtube.com/watch?v=pKKmzmeU5-0