Ariel's Grotto is a great place to catch her as long as you either a) show up early or b) don't mind waiting. As LAWalz23 mentioned, there's no real predicting who will show up when at the PSB. Last August, we had four princesses: Mulan, Aurora, Snow White, and Jasmine. Last week, we had those same four plus Belle. My advice is to do the PSB and if you're lucky, you'll catch Ariel; if not, then you can go to MK and find her there. BTW, we love the PSB: good food, great service, and multiple princesses. It's a real highlight for our young DD.