I live in St George and will stay in Snow Canyon (15 miles from home) when I get the chance. I also love Sand Hollow, but it is often booked by the Jeep crowd - Westside is the nice campground there. Quail Lake SP is pretty, no hook-ups and many sites are unlevel.
For commercial - Temple View is in town and very popular with the snowbird set. Over in Hurricane I like Willowind. The KOA is within site/sound of Interstate 15.
I would not risk Cedar City until April, as they're at 5,000' and could still be getting snow.
Best regards,
Chris