Is 18 months to 2 years too early for potty training, or can we start now?

Depends on child: It totally depends on each child. It certainly won't harm your child. Children with older siblings tend to learn faster but i throw everything out the window as to a definitive rule. Barring mental impairment, they will get it by kindergarten. You can try early if they are reading potty-training books, showing interest/desire, or save yourself all the work and in time they will do it when ready.

Perfect age: Many 18 month olds are ready to potty train. If your little one is showing interest , then start potty training with lots of praise!

When Ready: Many people have many indicators for readiness. The best sign I have seen is when the child wants changed every time they are wet, they generally can be trained in 2 wks. Although there is no real research, this seems to work.

Potty training myth: Parents training their children is a myth. They train themselves when are ready + want to use the potty. Let your child watch parents use toilet + offer a potty. If child voluntarily sits on potty you can make a shhhh sound simulating urinary stream hitting base of potty. Avoid negativity such as "ur2 old for diapers". Don't advise to "push it out" which causes straining via closed sphincter.