Generally speaking there are two schools of thought:
1) Children with Down syndrome will have the desire to communicate as well as the gross/fine motor skills necessary to sign long before they will have the oral motor skills to speak. So giving them tool to communicate is good idea that can prevent a lot of frustration on the part of the child.
2) Equipping a child with Down syndrome with a means of communication other than speech will hinder future speech development. Without the frustration of not being able to communicate they may not feel the push to do the hard work that is developing speech.
This is an over simplification of things, but each side makes valid points. I think it really boils down to what works for your family.
We have chosen to try to teach Lily sign language.
And for six months I felt like an idiot signing "eat" and "more" as she blankly looked at me and refused to eat. Over and over I mimed milking a cow as I offered her bottles of milk. I pulled my hand down my face for sleep every nap and bedtime.
Lily just blinked at me.
Then one day it clicked.
I was in the kitchen and she crawled in making her sleepy whiney noise. I asked her if it was time to go to sleep. She brushed her hand down the side of her head. I told her I would make her a bottle, and I noticed her little hand was clenching and unclenching.
She knew she was going to get milk.
About a week later I was laying on the couch, she cruised over to me, got right in my face, looked me right in the eye, she really made sure she had my full attention, and she signed "eat".
It was so simple, and it was amazing.
Her vocabulary now includes "eat," "sleep," "more," "milk," and her favorite "all done."
Every day we look up new words to use with her as we go about our day. "Bath," "chocolate," "celery," "popsicle," apple," "good". All my children are involved with looking up, and using signs with Lily.
Try as we might she refuses to sign "Mom," or "Dad."
The bad thing about child rearing theories is that you can't tell if your theory is yielding good results until the child is fully grown. I think that is why theories tend to cycle every fifteen years or so. Dr. Spock, Ferberizing, Attachment Parenting. It cycles around. So is this ultimately a good thing? Or in a few years will I be here lamenting about Lily's unwillingness to talk because it is easier to sign? Only time will tell.
Until we find out that signing was the worst thing we could have chosen to do I'm gonna be a proud Mama and show of video of Lily at naptime today.
And a little video from dinner.
Her version of more is evolving. I think it is adorable and so dainty. She didn't want to sign sleep because she didn't want to go to sleep.