You can pick which you want since you seat yourself ... if there is empty table. You get your own drinks etc. There are drink stations in every room.
We love the West Wing but it's hard to get a table. Our second choice is the Ballroom and we like to be by the windows if we can. Not a fan of Rose Gallery, it wasn't in the movie, is popular with young families and feels more chaotic and loud.
If you are having trouble finding a table in the room you would like to sit in, ask a cast member for assistance. Sometimes the "reserved" tables really aren't reserved. They are great about helping find somewhere to sit! After eating, make sure to take a moment to walk around and look at the other rooms. Enjoy!!!