We've just returned from a variation of this route, with bikes and their own GP  provided by a local company whom we can thoroughly recommend. There's plenty to see along this principally coastal route, Greek and Roman temples in Selenunte and Agrigento, great meseums and churches along the way as well as a National Park at Zingaro in the north and salt pans in the west.

Good public transport connections (buses coaches and trains) make strating and finishing from Palermo (as we did) pretty straightforward.