I dont't think it is too early to teach your child. But it would probably require many repetitions on your part and consistency as well.
My boy is 11 mths and he can understand simple instructions like yes and no. Whenever he does something undesirable like spray saliva or scream, I will say no very firmly. Sometimes he thinks it's funny and continues to do it but I will maintain a firm face and tone. After some repetitions (like 2weeks-1mth), he knows that he's not supposed to do it. After a while, he will try his tricks again and I will continue to say "no" (being consistent).
Kids like to test boundaries. We have to let them know the limits. Age appropriate freedom, that's what I call it.