I started potty learning with DD early on since she was showing many of the signs of readiness.
She has always been a big talker and as early as 15-16 months said, "pee pee potty", etc. She would ask to sit on the potty & I'd read her books and we'd sing songs. She went pee pee several times and poop once.
We really weren't having any progress though and I heard that the younger they are the longer it takes, so I decided to back off. That was about 2months ago. Now at 21 months I think DD is ready. She either brings me her CD or tells me poop when she has a dirty diaper.
I personally would rather wait to PL than have it take a long time.
I have a friend that started early and it took a year until her child was out of dipes. All children are different though and you have to do what works for you.
I say give it a go and see how works out. Worst case, you do what I did and stop after trying it out.