We started signing right away (3 months). We have two daughters (now 5 and 9) and we decided to commit totally to signing. It was painful and I cursed (******** I already speak 3 languages why do I have to learn sign language). Once I got it out of my system I put on a big smile and told the girls that we would all be learning a secret language and we started. I never told them it was for Kian. I bought all of the Signing Time videos and we all learned and used it. Kian (now 2) grew up with us signing. We continue to watch the videos every week. Plus, now we have an ASL tutor come into our house and tutor the family once a week for an hour. The big girl, my husband, and I can now do rudimentary conversations in ASL. Kian and the little girl drift in and out. They participate more when we do songs.
The girls were my secret weapon. My big girl now teaches all of her friends to sign. They think it is super cool and they sign to Kian. We all sign constantly to Kian. Kian also signs quite a bit - say 75% speech and 25% signing. Yesterday the girls said that they saw a dog and Kian signed black dog. It helps him get a "word" in with all of the kids! Also, what is funny is that whenever Kian hears the alphabet, he moves his hand like he is trying to sign the alphabet! I think it is because we are all working so hard to master finger spelling.