I would go ahead and start but not push things too much. If he understands “potty” when you say it, regardless of whether he can say the word, that is a signal for you to take some action. You can also help him acquire gestures that will temporarily serve as language. For example, if he pulls at his diaper, you can say, “Oh, you need to go to the potty” and take him to the bathroom. Do this even if you are pretty sure he has already done his business. Communicating with gestures even after an accident is better than no communication at all.
Unless you want a big plumbing bill, do everything you can to discourage him from putting toys in the potty. If he does that when you are near, retrieve the toy and say, “We can’t put toys in the potty. That is for our ‘wee-wee’ and ‘poo-poo’ (or whatever words your family uses).” And try to use his enjoyment of flushing as an incentive. Tell him, “When you learn to use the potty, you can flush it every time.”
Good luck. Just remind yourself that it’s much easier in this age of disposable diapers!
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.