Does anyone know if there is bus service to the south side of the island?  We will be staying in a condo there for the month of December 2009.  We were hoping not to have to rent a car for the entire time.

No, there is no bus service to the general public on Cozumel at this time.
There was one just beginning to get going but Hurricane Wilma interrupted and it never got back on it's feet.
mdp