Hi--I have two little girls that I use voice with. No sign language. They know a couple of signs for key words like "milk", "hurt", "sleep" to name a few.
Most of the time I can understand my little ones BUT I do miss out sometimes on three way conversations. When I don't understand, I let my girls know by saying I don't understand. Sometimes I catch it on the second or third try but the idea is to have the patience there. Sometimes I make my older girl tell me in a complete sentence what she wanted when she gets too "babyish" in communicating. She knows I can't hear like her daddy but that is no excuse to demand what she wants with one sign. I will probably teach them the fingerspelling when they are older but they need to keep communicating with the whole world. They're doing pretty well. Last month, my old best friend said my older girl who's only 3 3/4 is actually speaking better than her five and 1/2 yr old son. I was surprised by that. Never thought it would be that significant.
By the way, the kids are in bed within 15 minutes of going to bed or ELSE. This is Mama & Daddy's time. I know I sound like a bitch but that's what I am.