My dogs go outside, they let us know they have to go by "talking" not a bark, or a whine, they just chatter... but they also do this for other things, like they want the rotty to come in and play or eat, they want water, we forgot their treat after they went potty ect- so I may try and train them to ring a bell for potty.
Lilly, the puppy she goes outside, but she had to go more than mom and she didn't learn to tell us when she had to go she just went with mom, so we also had a pee pad out for her, which she used inbetween outside potty times.... recently though she hasn't needed it.
I think you can train her to go outside by slowly moving the pee pad closer to the door she will be going out of... also when you bring her outside to potty, don't play with her, and bring her to the same spot so she learns she is out to go potty, and give her lots of praise... then if you want to play move to a new spot in the yard so she relates the one spot for potty, the other for play.
good luck
