I own a camera store, so I hope this helps.
I was on the Grand Princess last summer and they do have a CD burner in their photo gallery. I don't remember exactly what they charged to convert the memory card to CD, but I'm sure it's less than $10.00 a disk. This is much more than walmart but still an inexpensive way to save your pictures and then re-use your cards, especially if you only need to do it a couple of times.
Memory card prices have fallen almost 50% since last summer, so you can now buy 1 gb cards for about $70.00. A couple of these would last most people their whole vacation, and you can still have them back it up to CD if you run short (unlikely for most people).
If you're a BIG shooter, buy a portable hard drive with card slots. I used one last summer and will use it again this summer. It is 40 Gigibites. They sell for $180. Every night I downloaded my cards, then erased them and shot again the next day on them. I then downloaded the portable hard drive to my computer when I got home. These are very small and eliminate the need for carrying lots of cards, or going up to the photo desk and making CD's. I shot over 3000 photos and still had pleanty of room left over.
If you have any questions, please feel free to contact me:
Best wishes & happy shooting.