I've only ever been on 1 cruise, so my advice may not be the best. That being said, there are plenty of options for western caribbean. You can depart from MIA, TPA, Canaveral, even MSY, MOB, Galveston, and probably more. Most cruises are 7 days, but you can find anywhere from 2-10 or so.

I would say as a general rule, Royal Caribbean is more of a classy cruiseline. Many different people from many different backgrounds, but overall more of an upscale type cruiseline. Whereas Carnival seems to be more laid back. If you want to party college style and not dress up for dinner, etc, Carnival is geared more toward that.

Pretty much all, and both of these, have an array of dining options. It's all included so whether you fill up on pizza or filet is your call. They have, of course, the main dining hall which is more of like a fancy restaurant. Most ships have other small, themed restaurants, like little burger joints or a small bistro. Most have some food somewhere all the time. And I think you can get room service at any time, I don't know if there is a charged fee, but you'll have a tip to pay. So pretty much on any cruise you'll have the option of a set dinnertime in the dining hall, but it is entirely your option.

Hope I helped a little.

Have fun on your cruise, I can't go on another cruise for a year, cuz apparently you can't go on a cruise w/o a parent if you're under 21. Well, I'm 20 and my mommy isn't as found of the adventures and detours involved in nonreving, and thus, only travels a little.