While researching our trip, we read many travel guides on the area. The most recent of them was dated 1994, with some older than that. You should be aware that the governments of the nations of "La Ruta Maya" (the Mayan Route) are working to improve things for the tourists all the time. Access routes are being improved, new hotels are going up, and museums are being built. The point is that unless your travel guide is really current, it may not tell you what you need to know. For example: we were driving from the ruins of Cobá to Chichén Itzá. One guide book I had read had said to drive from Cobá to Neuvo X-Can, and then on to Chemax, Valladollid and Chichén Itzá. There was a road that cut across from Cobá directly towards Valladolid (via Chemax), and on the map it looked like it would save a lot of time. However, the guide said "don't take that road, it is in terrible condition. Drive the more modern road via Neuvo X-Can". It sounded like a good thing to know at the time. While in Cobá, though, I asked about the "old" road and they said "Oh, that road was recently repaired. It is now MUCH better than the one to Neuvo X-Can!". So, we took the direct road, and saved ourselves time and potholes.
Another example: none of my research mentioned anything about a museum at the ruins of Copán, Honduras. There is a small museum in the town of Copán, but nothing was mentioned about a large one actually at the site. Imagine our surprise when we got to the Copán Ruinas and found a brand new large museum right there within the site! It contained many examples of building decorations that were from the ruins, and best of all, had a full-size replica of a Mayan temple, complete with colored exterior artwork. If you go to Copán, make sure you visit this new museum. We almost ignored it; from the outside it looks like a modern research facility or something.
A final example: I decided that I wanted to see the colorful Mayan frescoes at Bonampak. My travel guides said that you had to pay a tour guide to take you to near the site, and when the road ended you would have to hike the final ten kilometers through the rain forest to get to the actual ruins. It was not recommended for the faint-of-heart. However, when we were there the government was at that time putting the road all the way through to the site. Though unpaved, it was still accessible by vehicle, and the rain forest trek is no longer needed. It is recommended that you go with an official guide (easily arranged as a day trip/tour from the town of Palenque), as the cooperation of the local Lacandon (Mayan) Indians is required for what is considered by them to still be a holy site. The point I'm trying to get across here is: my guide said a hike was required. When I got to the region there was a dirt road right to the site. By now, the dirt road is paved and it is even easier to get there than when I was there. Things are being improved down there all the time. By the way, they were building a new museum at the site that should be done by the time you read this.