My two sons were delay in their speech because their first language were ASL. I was not really worried about this, they pick up really quickly with T.V. program and pre-school interact with other children.
Now, my sons are 22 and 21 years old, their speak are advance level than I expect. I am not really worried about the hearing babies with Deaf parents's delay speech development. I preferred, they learn ASL first language than speak to communication with me more effectively in ASL.