As stated by Katanya and others, there is no hindrance in "normal" children as you are saying the word with the action.

When you say"Bye" to friends and family, are you encouraging you child to wave? That's baby signing and the first indicator that they are ready to learn. When the phone rings, put your hand up to your ear like a handset and say phone... another Baby sign. Point to your lips when giving food and say "Food", Hold your thumb up and fingers curled into a fist(to resemble a bottle, or drink cup) and you have the Baby sign for "Drink". Very simple signs, allowing your baby when they have understood them to communicate their needs.