I'm pretty sure you'll meet a lot of interesting people. My friend went on that ship/cruise last summer and had a blast. They met alot of people also.
I went to Europe on RCCL in summer 2005 and it was pretty amazing. the ports were prolly the highlight...the only drag was waking up really early in the morning on little sleep. (depending on how late you chose to stay out with friends etc.)
When I went at the end of June, there were mostly college kids or older teens or very young ones. Everyone knew of eachother so that was also nice. there weren't really any cliques..there was a big group of PR
who just stuck to eachother. but nonetheless, for most of the groups that were made, you'd feel comfortable to hang out with them.