is 5 months too young?

If you use this method, then it's never too early. In fact, the sooner the better. Good luck!

when using the ec method, most start from birth. I started my first baby at 3 months and the second at 4 months. My first baby is now 22 months and pretty much potty trained. She still has accidents, but for the most part is pretty good.

what ec method?

I tried with my daughter at 6 months and with my busy life then, could not stick with it. I then started again at 18 months and my diaper costs were cut in half. I used disposable diapers.  She is 22 months and in panties.  She still has accidents, but I think it is because she is competing with her brother for attention.  He is 3 months old and I'm starting him with cloth diapers and diaper free time. His signs so far are very easy to read.  I'm excited about this new step.

My daughter has been ECing since she was 2 months old. Recently a good friend witnessed this. She had known we were doing EC but didn't know what to think. When she saw it in action she said, "wow, she wasn't traumatized or anything." I thought it was interesting that her first comment would be about how well my daughter handles doing on the potty.

 Autyme is just under 3 months and has been going to the potty every since she was 11 days old. Her big brother now 2 years started EC when he was 41 days old. I think the younger the better, but at any times good. The more cloth/disp. diapers we save the better. Personally I use cloth.