Know which ships are in port before you plan your day. If several large ships call on the same morning, the Old Town, the City Walls and the cable car all queue up between 09:00 and 13:00 — and that is exactly when a private driver saves you the most time.
Schedules change with weather, itinerary edits and port allocation. Check the official Port of Dubrovnik announcement and your ship's daily programme before you plan a tour.