Do not torture yourself at the ruins at noon, which was what we did after sleeping in due to the bus ride that was 4 hours longer than expected. Beware of the bus route for ADO that loops to Tobasco from San Christobal to Palenque instead of taking the 3Hr route straight. We arrived at 2am, tired and confused, unsure of the reason. My Duolingo Spanish got me a reply of “Solo Una Ruta”, and my guess is that the more straightforward path had an issue/blockage at the time I was there (March 2016).
Walking through the city at night gave us the impression that garbage was not cleared regularly, and our overpriced budget hotel smelled musty. Another option would have been to take a tour from San Christobal, stopping over at Agua Azul and Misol-Ha that would finally end up in Palenque. However that is equally trying as the pickup is at 5am and you would end up at Palenque in the afternoon steam.
After 2 fresh coconuts, I was still close to heat exhaustion in the ruins, and we gave up climbing up to the top of every one. They are very spectacular, and are worth the mind numbing humidty, but do yourself a favour and go at dawn.
The Aluxes ecopark was a nice stopover back to the city, and there are many collectivos plying that route to hop onto. Limit your time in Palenque, as the town itself is not quite welcoming.
The horror continued when the ADO bus scheduled to Merida for 11pm arrived at 2am just as ours did the night before, and the uncomfortable chairs at the bus station did not help. That was the only time ADO had let us down, but it was huge.