Yes. There's no way Batman could ever hear about Joker hanging out in some other city without taking off after him. Poison Ivy, maybe, but not the Joker.
And on that note, it's sort of weird for the Joker to leave Gotham at all. I know he's done it before, but that always seems to contrast badly with his Batobsession. I really can't see him giving a damn about Diana, except possibly as a way to bother Batman.