When is spring break, April?
Southern Utah would be awesome.
You never know what you might get up north.
We were there last late April and early May. It was a storm in SLC that turned to snow in Logan Canyon. Snow was only around for about 4 or 5 days, but we had CLIMBING to do so we headed up to City of Rocks early.
A lot of mountain roads in North Utah are still closed that time of year.
The road to the North Rim of Grand Canyon would be closed until sometime in May, but you can get to the South Rim.
Awesome trip!!
I've got a guide for the Moab area you can borrow.
Elsewhere
Mid March for Indian Creek is about the earliest I've been there, a bit chilly at night. Plenty of southern exposure cliffline once you motivated. Drawback is the rain can be tricky if you are planning vacation that early. March can be perfect, it also can rain for a week solid. Things calm down first part of April plus the bonus of longer days. It might rain for a day or two, but typically it clears up then. 
End of April into May is just about perfect, even longer days, stellar weather. Climbing in the sun in the morning then following the cliffline to shade in the afternoon. It also turns green in the desert in April, (that is, all the green Colorado license plates!)
End of April into May is just about perfect, even longer days, stellar weather. Climbing in the sun in the morning then following the cliffline to shade in the afternoon. It also turns green in the desert in April, (that is, all the green Colorado license plates!)