The visitor's center and Temple of the LDS church is a nice facility where you can pick up a little history and see the outside of the Temple. However, you will likely be subjected to a mild version of the history of the LDS church and their views. Also, you can't go in the Temple. I think you can learn more by just reading information online and visiting other sites in St. George.
If you own or manage St. George Temple, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.