I live in the area, you should have a pretty good tailwind most of the way. I have done the St. Andrews to St. George leg before, I can give you some advice on that route, you won't want to go the Google Maps through there, stick close to the water through the city, much more pleasant.

Watch out for Racoon's at St. George SP, did battle with them all night all over my bike, bags, and had teeth marks on my food containers.

wsgts