Are there busses that leave from Nuevo Laredo Mexico and go to Cancun Mexico?

Yes, but you need to go thru Mexico City. there are many lines from Nuevo Laredo to Mexico City. when you get to Mexico City, Take ADO to Cancun..it is best...tho there are many others too. Buses leave freq. from N.L. to M.C. and from M.C. to Cancun, so don't worry about shedules. Your wait should be short. Just go to the ticket window for info. when you take a bus from N. Laredo to M.C., be sure to take one that will go to the TAPO station as that is where the ADO buses leave from to go east.