Does signing with children delay speech?

No, signing will not slow down the development of speech. If you break
down the way we communicate into three simple parts: 1) sign language that
happens at your hands; 2) language (knowing vocabulary and how to put
words together) happens at the brain; 3) while speech (the sounds you
make) happens at your mouth.

The motor skills needed to use signs develop before the motors skills
needed for speech. If you think of the word “spaghetti”, the sign is
easier to produce than the spoken word for young children.