This is a personal decision since the only person who really shouldn't see the dress before the wedding is the groom.
It is a good idea to bring along a few friends or family members when you are trying dresses to get opinions but for the most part I would suggest telling all others that you do not want to bring along that they will have to wait for the big day to be surprised.
In short, only those you want to see the dress should. Top Wedding Questions Forum Moderator - "Write your sorrows in the sand, your blessings in stone".