Yes you can ask for a table for two before sailing but there is no guarantee. Also there's a welcome onboard news letter in your cabin on embarkation telling you when to visit the MDR to book a table for the whole duration of your cruise. However you have to eat early and vacate it before 7. 30pm on a full cruise so if you like to eat early do that. Bear in mind some of the tables for 2 are almost touching the next tables with very little space. The first night of your cruise you are told where to eat and time for a smoother service. However should it be a speciality restaurant you don't like you can change it