I belong to a site called "cruisestateroom.com" - it was really cheap to join and more than worth the cost. You get deck plans and floor plans of every major ship in the US cruise world.
I don't know if they are downloadable - but you can print anything you want. Why do you want them downloadable, anyway?
I am the editor, but I also speculate, ask questions and play devil's advocate. I reserve the right to change my mind.