I think that's a great idea too, I would love to bring bikes to the islands. I'm sure it can be done, you won't believe what I saw being driven off an RCCL ship in the caribbean...choppers, big, loud, obnoxious motorcycles tearing up beautiful St. Martin!
I read about this in the NY Times recently, RCL is offering theme cruises and they had a motorcycle group cruise. All the bikers brought aboard their Harley's, stored them in the hold and rode them off on the islands, and I can't believe I actually saw it. I can't remember which ship but it was this past April. Great. ;(
If they can fit those choppers onboard than surely they can bring aboard a few bicycles.