My youngest is now 2 and we have been potty training him since the age of 6 months. Well...more my husband than me since I can be completely lazy in regards to this. "Kai" would be put on the potty every couple of hours and while he was on there my husband and I would sign and say "potty". After a while my son would start to wave his hands as if he were signing "potty" - which really amazed us. His "potty" and "hello" really looked similar to each other so we would label it and boy.... did we take him to the potty plenty of times after that! But you know what? Each time I thought he was just saying "hello" and did not place him on that potty he would do his number 2 soon after that. That certainly taught us a lesson. He has pretty much been potty trained in the "number 2's" for quite some time. However, he has been regressing lately and hiding from us when he does. Hopefully, that will change soon.
Although, he is verbal I still sign with him. He thinks it's a lot of fun! And yesterday while he was on that throne we sang and signed "ABC" about 10 times. More on that another time. =)