It's become a custom for Autumn and I to spend weekend days (before and after the roller coaster rides, of course) people watching at cafes.
The Paris Baguette near Kyungsung University is an excellent venue, as it offers sandwiches and salads as well as tasty sweet things, and on very hot July days it is also air-conditioned.
(That delightfully shiny ring-o-balls on my tray is a mochi ring, which I highly recommend if you ever come across them in the States. They have them at Mister Donut and Dunkin' Donuts here, but I don't know if they do over there. It's chewy and sweet in the same way that you'd imagine Hello Kitty is chewy and sweet.)