I am struggling with a similar situation coming off the Dawn. We need to get back to FLL to get the car we have rented (Iknow you can rent a car anywher, but not the kind we want and we'll be in FL for 4 days so we want a particular kind).
Here are some of the options we've been exploring.
1) Cab- about $60, quick and convenient
2) Limo - most expensive, requires commitment ahead of time, but really nice!
3) NCL transfer- cattle call, slow, around $50 for two one way?
4) Trains - Not sure of schedule or where you pick them up, but they are cheap. Probably a pain to handle your luggage on them. Safe?
I'm still working on this and will update later. What have you found so far?