There is a small building in the centre of town, next to the childrens play park. You can't enter it, but just approach the window at the front.
They can supply you with a bus time table.
Much to our surprise, they also gave us a glossy 100 page soft back book called 'Greek Islands Dodecanese' that contains details of itineraries, history, photographs and maps of the islands - totally FREE. Worth calling in for the book if they have any.