If you don't find out until nearer Lisbon text your friends when you know for certain the correct one, I think like Celebrity RC has the facility for you to use your mobile at sea but don't get carried away it is pricey, so stick to text.
Why don't you email Royal Caribbean and ask them? Most ships dock at a couple of different places in Lisbon depending on how many ships are visiting that day, so it is even possible for berthing information to change at short notice! However, with the Independence being so large, I should imagine that Royal Caribbean will be able to tell you for sure in plenty of time. Happy cruising.