+1 for flying to and from CZM. The airport is small and easy to manage, and it is right outside of town. Even if you're staying on the north or south coasts, nothing is far away in Cozumel.

Many Cozumel residents and expats do what they affectionately call the "Cozumel Bag Drag" for their travels to and from the island: Fly to CUN, bus it from the airport to Playa del Carmen, and ferry across to Cozumel. CUN has so many more flights than CZM that competition keeps airfares cheaper. Those people have the time and experience to be able to do this. For a limited-time trip over the holidays yet, I say avoid that, and get right to Cozumel.

Enjoy the island. I think it's a wonderful place.