I have had a few kids whose parents used sign language and found it had no relation to how early/well they talked. I have one 17 month old who is an amazing talker and he also has some signs and will use them while talking...it hasn't hindered his speaking at all. I have another recently turned 2 year old who is only now starting to speak a bit and I wish I had started using signs with him eary on so he could have at least communicated some things. He is also behind in many ways, but parents coddle him, so it could be that or simply genetics...some kids do things earlier than others. He is progressing, so I think he will get there in his own way.