Absolutely! I am an Interpreter for the Deaf and involved in the Deaf community as well as teach ASL to hearing students. When we had our first child we immediately started teaching her ASL.
We spoke and signed at the same time beginning at two months old. At ten months old, she began producing signs. Studies show that it helps speed up the desire to speak, increase vocabulary both with sign and spoken English, and increase conceptual skills.
We have witnessed all of this.Its amazing!