The coast road from Cancun south to Tulum is a big divided highway with lots of traffic. However, there was a good paved shoulder, so the cycling wasn't too scary or that unpleasant. I don't have a map in front of me, and I don't know precisely where Puerto Aventuras is on the coast. Here are a couple of cycling possibilities:
The ride around Cozumel was fairly nice and an easy day trip. Also, we headed inland from Tulum, and the ride from there to Coba was pleasant, with minimal traffic compared to the coastal road, and mostly riding through vegetation.
One thing to know is that it's very easy to throw your bike on most buses in Mexico. We flew in and out of Merida, and took a bus from somewhere south of Merida (near Uxmal) across the Yucatan to Playa del Carmen, and biked back to Merida.