The downtown Milwaukee River bustles these summer days with boaters and kayakers and cruises, while people on shore sit at the cafes. It would have been difficult to imagine a few decades ago, when the river was still largely an industrial dumping ground, but things started to change when the city developed the Riverwalk. It now spans miles. Yet one small part of the dream has not taken hold - the creation of river taxis. Signs are posted, but no taxis.