The following itineraries assume you're flying in and out of Cancún, by far the most common port of entry for the Yucatán. The airport is south of town in the direction of the Riviera Maya, so if you rent a car to drive down the coast, you won't have to deal with city traffic. For traveling around the Yucatán, rental cars work well. The roads are all easy to figure out, and there's not much traffic when you move inland. Finding your way around Mérida is a little tricky, but Cancún and the other cities of the peninsula are easy.
These itineraries are merely suggestions; you should tweak them to your specific tastes and interests. However, I recommend against being too ambitious with your vacation time. The heat and humidity bring about a lethargy that can be enjoyable if you're not preoccupied with a timetable. Keep in mind as well that it gets dark early here, and it's not a good idea to do much night driving.
