I just returned yesterday from my first ever cruise. It was an interesting experience and one in which I would like to share to hopefully help others out. We are in our 20s if that helps make an age-based opinion.
We chose to book a Carnival cruise at Port Canaveral because the port is very close to where I live which made the choice easy for us. Like I said, I had never been on a cruise before so I relied on reviews from this website as well as from some friends who have been on cruises before. I was told that the Carnival cruise ships are not the most luxurious of the cruise lines, but that they have a good mix of people on them and that they are supposed to be The Fun Ships as their slogan states. Our cruise definitely did have a good mix of age groups and we did have a fun time aboard the Fantasy (for the most part!).
We got a VERY good deal on the price of this cruise by booking in December of 2005 because Carnivals website had a special running called the 12 Days of Christmas. They took $100 off the price of the cruise for each of us which was great! The one thing I wish I had looked at more closely was the itinerary because we did not spend a great deal of time in the ports. More on that later.