I actually think my daughter learned quite a bit of verbal language from signing time (although, obviously one person's experience is not a scientific study)- if she just signed a word... "shoe" was a favorite of my daughter I would always just reinforce that with lots of language - "Do you want your shoes? Where are your shoes? Can you say shoe?" Then I might ask her to say it. She was a great early talker and I think that being exposed to lots of forms of early language was helpful. We also had lots of story and nursery rhyme CD's - might get her away from the signing...