Basically it is a meet and greet. Last I heard, they called you back if they wanted you for an interview in Salt Lake. When I attended the group interview in St. Louis back in August they invited everyone who attended to Salt Lake for an interview. I have heard that has changed, so I don't know what they are doing now. I know of a few people on hear who have attended recently, hopefully they can give you more insight.
Anyways, I have been extremely happy here after coming over from another 121 carrier and wish you the best during the interview process! Just try to remember that SkyWest is actually worth all the hoops they throw you through during the hiring process.