My daughter lives in the St. George area. There are some good road bike routes in St. George. One of my favorite is to take Snow Canyon Parkway around to Center and up to Kayenta. It circles around to Old Hwy 91 and you can either circle back or go through Santa Clara. There is also a great ride going out to the airport, Sand Hollow Lake, and back to St. George. There is a big hill climb going out to Veyo, it does circle back and you get a nice downhill on the way back. If your staying in Hurricane, (pronounced Hurricun) the road out to Sand Hollow Lake and to the airport to St. George and back would be a good ride. I'm not a mountain biker, but there are a ton of mountain bike trails around the St. George area. Good luck and have fun.