You can ping wifi from the resort so if a lot of your guests have iphones they can imessage each other, or you can check facebook. Otherwise when you dial 0 sometimes they will give you room numbers if you tell them you need someones room number to call them and other times they say they will transfer you but won't give you the room number so then when they pick up just ask their room number. I kept a list of everyone's numbers on my phone. We had a meeting spot on the beach where everyone went if they were trying to meet up with the group. I did not try going to the front desk to get a list of everyone's rooms as I felt like that would take hours to get accomplished. If all your guests book together (ie with your TA like mine did) everyone will be close together and everyone will be in the same sections. Hope this helps!