This is not the easiest guide to teaching a hearing baby to sign, but it does have lots of great ideas for fun activities to do with your toddler while teaching them.
The only outright disagreement I have with the authors is their assertion that parents should teach ASL signs only, with no modifications to accommodate for their limited fine motor skills. This is expected given their background in ASL, not child development. After signing with all 3 of my children, I feel you should use ASL whenever possible, but be flexible enough to meet your child at their developmental level when they are unable to do a few ASL signs. You can always teach them the ASL sign later on when their motor skills improve (as we teach them "tummy" and later teach them "stomach").
This program is targeted to families who are planning to continue to use ASL past speech development, rather than just for pre-verbal babies.