it usually depends where the fight is being held.
Sometimes if its at a nice arena that has a conference hall, or media location they will do it there. Sometimes the location of the fight has a contract with a local hotel to promote the fight,and the hotel will have the contract to hold the weigh in, and pre-fight conference. You can call the office of the promotion company handling the fight, they will tell you where it is, if it has been decided.
Good luck! take pics!