Hello,
I also taught my little girl to sign. We didn't start trying until 6 months old and she really never started until 8 months. I have heard of babies signing at 6 months of age. I think it all depends on the child. All I can say is that it has saved us alot of headache...all she has to do is say what she needs and if we can't understand then she signs it. It has been wonderful in our house!!! Good luck!!