Training wheels will hinder the ability to learn to ride- as they teach one to do things which are counter-productive to balancing.

It takes mere minutes to teach a child (or anyone) how to ride a bike.

Balancing while in motion, isn't really something that needs to be learned; it's something we can all do, naturally. The trick is, just having the confidence to do it the first time; same with swimming.

I still remember learning to ride a bike when I was six! [I was taught by someone named Fred, ironically!]. The guy just held the bike up from behind- so that I couldn't see him....and after a little while, he let go- and I was riding! I was amazed when I looked back and saw that he wasn't holding the bike! Seriously- it takes <5 minutes to treach a kid to ride that way. Of course, once they learn to balance, then you can explain some of the finer points- like about wet leaves and sand/loose gravel; ride as if you're invisible; and all that.......

It seems, everyone I knew who had training wheels, ended up taking years to learn to ride on their own...and even longer to become competent and confident.