I went on Carnival Inspiration over Spring Break 09. I turned 18 the day we boarded and was still a senior in high school (since it was the end of March/start of April), so I wanted to be in the Club O2 still one last time (I figured if it was boring I could easily switch to the adult club).
HOWEVER, there was a group of about 10 guys that came for their grad cruise. 2 of the guys had already turned 18 a couple months earlier and she kicked the 2 boys out even though she let all their friends in Club O2. She explained that if your birthday wasn't within basically a couple days-week of the cruise starting she wasn't admitting any 18 year olds.
I have no idea what ever happened in the adult club, but I did talk to a couple of kids 18-21 at the very last night for a second and they said the club had been a ton of fun all week and I should have gone. lol
It looks like you are good to go either way. I'm now officially in the 18+ up group, so I'm right there with ya in the adult clubs although I won't be cruising for a long time now anyways. haha I'm sure you will have a good experience if you are cruising over summer or spring break which attract tons of young people. 8)
***Lauren*** Myspace & Facebook (firstname.lastname@example.org)
CRUISES I HAVE TAKEN SO FAR...
Disney Wonder (2003)
Carnival Inspiration (2004)
Carnival Victory (2005)
Carnival Miracle 2006-2007 (New Years Cruise)
Carnival Liberty (June 9, 2007)
Carnival Glory (July 5, 2008)
Carnival Inspiration (March 28, 2009*18th birthday Cruise!!)