Okay, apologies for the previous response. Just a tad inappropriate, and I was on my cruise all week last week, so no opportunity to reply to this or moderate...
Anyways, Yes, you will meet people. The concern I hear a lot from inexperienced cruisers is whether they will meet anyone. If you are outgoing, you will meet people. Enough said there. Just put yourself out there, introduce yourself, and have fun.
Go to the teen thing on the first night. Teen club is very clique-y and the cliques form from night 1. Don't miss out.
Be outgoing - show your personality, or be someone else. It is a cruise. Have fun with it; there are no consequences.
Try new things. Eat something new, do something crazy.
Sadly, I cannot comment on Disney cruise line as a whole (particularly Vibe since its new), but I'm sure there are people out there who have been on who can.