I disagree slightly with choochoo. We've done the bus from Cancun thing several times, and it certainly is CHEAP. You get what you pay for, the ride is interesting though. So, its a matter of perspective. If you're the kind of person that doesn't care if you have to schlep your suitcase on and off a bus in the pouring rain, then go for it! Its not bad, its not quick or luxurious either. Just makd sure you take the Premier Class (First Class) bus or the normal trip of 5 hours to Chetumal could take you 8 hrs. I've met some very interesting people on those trips.

--http://www.caribbean-colors.com