I have a 3yr old female Yorkie and just brought home a rescued 1yr old male American Bulldog. He is very gentle but prone to chasing anything that moves. My Yorkie is actually the one that is more aggressive and she has already caused an "incident." Just as a safety measure, I would not suggest getting a Yorkie. If thinking of another dog get one that wants to play with the bulldog. It would be the best thing for everyone.
you would be better off if you already had the yorkie before the Am bull, Am Bulls are good with littler dogs if they grow up with them, not a good idea to get now because of the Am Bull's natural prey drive Same deal with cats,ferrets, exc.