He says quite a few words (which was a HUGE concern of my in-laws when they learned that we were doing baby sign w/ my son...they were worried that he'd be delayed in learning to talk because we were teaching him signs as well). No worries there, though, for he's shown them that this wouldn't be the case. He says: Bye-Bye, Dada, Mama, Nana , Book, Brooooooom (for cars or trucks), Uh-oh, KiiiiKii (kitty...or any other mid- to large-sized animal), Nigh' Nigh' (meaning both "night-night" and "nurse"), Boom! (when he falls), and his newest...NoNoNoNoNo!
He also uses a lot of baby sign, and can sign eat, drink, more, all done, down/up, please, light, diaper, bath, and fish -- which refers to fish as well as any other small animals, such as birds or chipmunks.
I just looked up the signs for some other words, and will start introducing them to Sean next.
Help me, hurt, and sleepy are three that will be very helpful for both Sean & I to know & use.
He's also facinated with birds & dogs, so I looked up those signs. And I looked up the sign for water -- whenever Sean sees water, whether it's a lake, stream, river, ocean, or even just a puddle -- he points at it, looks confused, and finally signs "drink!"