Sorry not much help... dd is 3 and 1/4 and just been telling us for a short time. But ds is 22 months and tells us "pee" or "potty" when he
wants to go. Now we don't have him in underpants and so he uses his diapers still a lot, and sometimes we go to the potty and he doesn't
'produce.' But he is really eager to go try, so I am just glad about that. I should probably start putting him in underpants and see if we have any
luck 
I started letting G be in underpants when we went out when she would comply with trips to the bathroom when we were out, and when she wasn't having many accidents at all at home. So probably right around age 3. (She was good about going to the potty when we were out before she was not having accidents at home... she used to be scared of foreign potties but then it became fun for her to see them, so she was great about it!) Sometimes if we are going to be out for a long time -with lots of driving, I will still put her in a pull-up.
I started letting G be in underpants when we went out when she would comply with trips to the bathroom when we were out, and when she wasn't having many accidents at all at home. So probably right around age 3. (She was good about going to the potty when we were out before she was not having accidents at home... she used to be scared of foreign potties but then it became fun for her to see them, so she was great about it!) Sometimes if we are going to be out for a long time -with lots of driving, I will still put her in a pull-up.
