The ships we have sailed on (Princess, RCCL and NCL) have all had doors between the cabins on the balcony's. My brother and sister-in-law are always in the cabin next to us so we get the door opened the first day of the cruise. You cabin steward has a key to unlock them. We love being able to pass back and forth without going out in the hall. Also we sit out there on the balcony and just chat. It's wonderful. Just be careful if you plan on this occasionally there are structural beams that will prevent a door in the balcony. We always check with the cruise line that the cabin balcony has a door. They have individual room descriptions ..... you just have to get a knowledgable custom service person.