Hey JLM,
We're on board same time as you are. Been to St. Kitts before, the beaches are very nice, shopping is pretty good. Is this your 1st cruise? Princess provides a pretty detailed port info package the day before you get into port which may help.
From what I've read on this and other boards, Isla Margarita is either a waste of time, or a great time. I'm thinking we'll get off theboat, have a walk to a beach and maybe do a little shopping - its a half day after all.
See you on board.
Pete