Stay in school.
OK...Yes...the Student Union is noisy but...it's meant to be.
If you want somewhere quiet...Please walk your butt over to the library.
I think the UNLV Student Union is great. The first floor is set up very much like a food court with popular choices like Panda Express, Jamba Juice, Metro Pizza, and etc. The lines can get pretty long at peak lunch hour but that is expected when there are so many students that congregate here. There is also a Starbucks that get's insanely busy at all times. There is a game room with a pool table and your typical arcade games.
The second floor is quieter and is where you would want to go to get some before class studying done. There are couches, study rooms, and a computer lab available for students to use.