This was me and my girlfriend's first cruise and we were a bit apprehensive about it, as normally we travel independently. In summary it was good though.
Booked cruise online using cruisedirect as enabled us to book at US prices, rather than UK prices which were significantly more expensive. Also enabled us to choose exact cabin which the UK website didn't allow.
Flights to San Juan booked with American Airlines, from London Heathrow, via New York on way in, and via Miami out. They allowed free stop-overs so we spent a couple of nights in both those cities which was good and made the holiday about 2 weeks in duration.