I took a 15 min ferry ride from Isla Mujeres to Cancun Puerto Juarez ferry terminal. The round trip ticket was $15 USD or $300 Mexican Pesos.
From there I took an expensive ass cab ride to Cancun ADO Bus Station. Im just kidding, its not expensive, but expensive via mexico standards. The tourist price was $100 Pesos, which is $5 USD.
Lets take if from the ADO Bus station. From the exit you must make your way to the other side of the bus station, towards the giant round about. Now cross the roundabout. It has no street lights so be very carful as you cross all intersections.
I did this carrying my backpack in the sweltering heat… I got lost, asked several people took the long way around and finally got there.
Here is a map so you could find your way. Don’t do what I did. Lets attack the problem at its source… Lets get you on the right track.