Nicki dahling,
On the past 2 cruises I have used mainly 400 speed film, with some 800 thrown in. It is what I am most comfortable using so I wasn't about to switch. Also it is fast enough to capture movement.
A couple of thougts - if you are using an SLR camera with interchangeable lenses (which I do) you'll want a polarizing filter for outdoor pictures. Practice using it at home on a couple of rolls if you've never used one. Most of them come with a little arrow on the outer ring that needs to be pointed towards the direction of the sun or you get some "interesting" flares! Just remember to take it off when you go inside! I couldn't figure out one day why it seemed SO dark when I looked through the viewfinder....DUH!
Also keep in mind that many of the interior areas are large and softly lit. The built in flash on most cameras just won't fill that much space. So anything very far from the camera will fade out into darkness. Much in the same way it would in a church or gymnasium. Again if your camera allows investing in a shoe mounted flash will add length to the flash ability.
If you're using the point and shoot pocket variety of camera then I'd suggest smaller rolls of film, possibly even as small as 12 exposures. This will give you greater flexibility in switching between faster (800) film speeds indoors and slower (200) outdoors since those cameras don't take a filter.
Mind you I am not a professional, just someone who has played around a bit with my cameras and these are things I've discovered over time.
If you're looking for a great film source checkout
www.bhphotovideo.com. Excellent prices - but you want to buy in quantity or the shipping fees could wipe out the savings.
Deb