You may be able to also print them out. Last time I just had to e-mail them and they sent some tags, but I understand, they no longer do that. If you don't print them out, yes, you can get some when you arrive at the port, just ask the gentleman that handles your luggage and he can point you in the right direction.
Also, make sure you go to Royal Caribbean's site and fill in all your information. What ship will you be sailing on?? You may be able to also pre-book shows and alternative restaurants as well.