I have travelled around Mexico a few times and always catching long distance buses. I find it easy, cheap and a good way to travel.
ADO, the largest bus company in Mexico, covers the whole country – some parts more than others – and you can even buy tickets online in advance. I used www.ado.com.mx/ado2 to check travel times and www.clickbus.com.mx to buy my tickets. In one occasion I decided to change my date of travel and changing ticket at the ADO station was a quick and smooth process.
Long distance ADO buses are very comfortable, with wide seats, lots of leg room, TV, a/c and toilets on board. They are also reasonably priced: a first class ticket from Cancun to Chetumal (6hrs) cost me less than MEX$400 (around £14)!
I caught ADO also from Cancun airport to the main bus terminal in town. The airport bus service runs every half hour and takes around 35min to town. For MEX$70 it’s a much better deal than any form of private transport (taxi or hotel shuttle).
When I was in Bacalar I then discovered another bus company, called Mayab. It is part of the ADO group, serving mainly the states of Yucatan and Quintana Roo, and provides cheaper service than the main ADO. The downside is that buses are not as good and travel times are longer due to the higher number of stops, yet they offer a valid and cheaper alternative to ADO. Tickets can be bought online using the ADO website or at bus stations themselves.
And how about the experience of travelling with lots of local people and discovering the country at a slower pace?!