I’ll admit that my view is somewhat coloured by having fallen off in a motel car park there and ending up in the OR having an op to reseat a finger thus missing 5 days guided mountain biking in Brian Head but St George is not a place you would want to spend any time in.
It’s kind bland suburban sprawl’n’mall with no character.
Obviously can’t comment on the cycling… 🙄
I’ve heard good things about Bryce and Zion though (scenery is certainly stunning).
You would probably get more help on here: MTBR – Utah Merkins tend to be super helpful…
Moab has buckets more going for it atmosphere wise though (IMHO).