You can just check your luggage in with the porters at the pier. As Dave stated, you should be allowed to board before noon, but your rooms won't be ready until around 1:30.
On my most recent cruise, (Enchantment of the Seas), I landed at Fort Lauderdale Airport around 11:30 am the day of embarkation and was on the ship by 12:30 pm. This was a 5:00 pm set sail from Port Everglades.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas