I put in a selfish vote for Sedona, Az - Arizona born and raised here.
Sedona will be absolutely beautiful temperature wise at that time of year ... Phoenix and Flagstaff are both within 1-1.5 hours drive. Of all the places I have been in my lifetime, Sedona remains my favorite.
If you are looking at west Coast, another place you might consider is Kenwood Inn, in the Sonoma Valley
http://www.kenwoodinn.com/
A friend of mine went there for a weekend vacation once and told me that is where she chose to go on her honeymoon - from seeing the pictures, I can certainly see why.