i think every child is different in this regard. my DS was not a great communicator regarding elimination, and we went mostly on timing until he could talk and tell us he had to go (IIRC around 15-18 months was when that really clicked with him, i remember very clearly by 18 months he could tell me and take himself if he was nakey). my DD2 started signalling the day she was born, and has always been amazing at letting me know that she had to go, though her chose manner of communication has changed as she has grown. once she really started talking about 2 months ago she says "pee pee" or "poopy" but prior to that she grabbed her diaper or ran for the toilet, prior to that she crawled in the direction of the bathroom, prior to that she would fuss when she had to go. i started with my DD1 later (9 months) though i now look back and realize she was a great signaler as an infant, she had abandoned those signals by the time i started EC with her, but she loved signing so she started signing potty before she could say it, probably around 10 or 11 months old IIRC, plus she was an early talker so it was followed soon after by telling me "potty" or running towards the bathroom.
