Buses will carry bikes in the undercarriage and go everywhere. We used first class buses, which are like Greyhound. We traveled light with no camping gear. Camping available at Merida, Uxmal, and most places on the coast. One possibility is to buy a hammock and blanket in Mexico and use this at campgrounds.
Roads are two-lane, paved, literally no shoulder at all.
Drivers are cautious, slow down if they can't pass and give bikes plenty of room. An edition covering only Yucatan is also available. Great for transportation schedules, hotel and campground listings. Complete descriptions of 24 sites in Mexico and Guatemala. Good background on travelling and living in Mexico.