Go for it!!!
No, seriously, I would really recommend it. I signed with my DD and I am a huge fan. Started at about 7 months, byt she didn't really get into the flow of signing properly until about 11 months ish. Then it snowballed.
Within a few months, she was able to sign all manner of words, and ended up being well over 100 signs, but then she learnt to talk!
But she could sign about all sorts of things, including to ask for the light to be switched on, she could sign pain and sad and all sorts. I will definitely do it again.
DD is now 26 months and her language skills are very much advanced fro her age. It is not uncommon for her to use 8 word sentences, she understands me, he, she her, mine etc and can say some very complex things such as 'take away now daddy, put in the bin'.
I did find in the early days that perhaps she didn't speak as early as some other children might do, because it was easier for her to sign, but I found that once she got going with talking, she just did it and learnt to say a lot more than a lot of her peers.
Signing has definitely helped her to learn to talk. She hasn't signed now for months and I don't think she remembers that she ever did, but it is so lovely just being able to have a conversation with a 12 month old, and get to know your child in a way that you just couldn't do if you didn't sign!
(Sorry for the very evangelical post, but believe me it is a truly amazing experience!!)