Clearwater Beach is beautiful and our favorite. It is much less crowded than the others.
I would take the suggestion of getting a taxi from St George rather than a bus. It is in a remote area and the buses as mentioned, can be unreliable with long time stretches between them. Add this to the time taken to pick up and drop off passengers, and you are looking at time wasted.
And depending on which bus you get, you may get dropped off at the top of a hill with a long walk down to the beach. There is a bus stop close to the beach, but not all buses come down to it.