If manners are important to you and your family, than signing is a must. Manners can be taught as a habit and begin as early as you can teach signs. If you want your young toddler to use them, then just incorporate them as part of your early signing program and they’ll soon become part of your baby’s vocabulary. As far as they are concerned, it will just be something they’ve done. Besides it’s nice to get random THANK YOU’s here and there and PLEASE when grandma is around to show just how well you are doing as a parent.
I wouldn’t recommend that manners be the very first words a baby learns, but certainly they should follow the words which are most important to your baby. MILK, EAT, MORE are the signs you probably want to start with since they matter to your baby – they have currency and are likely to be learned quickly. Manners on the other hand, have currency to you and will come with time. When teaching manners, you always want to lead by example. If your baby sees you use manners, they will too – but if you don’t then neither will they, unless asked. This isn’t to say that manners don’t first begin through prompting, because they do, it’s just that to have them continue, you need to be polite too. When making requests of baby, don’t hesitate to add PLEASE and THANK YOU even if your requests aren’t optional. That doesn’t mean you have to beg, it just means that you shouldn’t be rude. If baby still doesn’t cooperate than use a more physical approach by completing the task by moving their body however it is you wish. Children are excellent at copying what they see, so if you’re rude and demanding and show no courtesy for their desires, then neither will they, to yours. However unfortunate this is, it’s just how things work – at least how I see it.