It is highly recommended to get an early start, leaving Flores at 5am if you are not staying at one of the expensive park hotels. This way you have time to climb a temple before the sun rises at 6am, hear the jungle wake up, and beat the heat. Keep your eyes out for the exotic wildlife crossing signs and animals along the road into the park. Only buy your ticket from the official booth yourself for 50Q, which is about $7. The park map is a good deal and the translations into English are quite humorous in parts.
At that hour of the muggy morning, I descended into the jungle alone, listening to the birds squawk and waiting for the howls from the monkeys. The first time I heard the roar from a full-grown male, I about jumped out of my skin from the primal and guttural sound. Head back and eyes to the tall trees, I witnessed several howling matches, monkeys crashing down branches, and fruit being cracked open, then the shell hurled at gawking tourists. This was my first time seeing monkeys outside of a zoo, so I too was in awe. Other wildlife highlights include a colorful wild turkey and a toucan.
This is an impressive Mayan site in the size of the temples and steep steps. To see the view in the photo below, I climbed over 200 wooden steps to reach the top of the temple. There were several that were so steep that I would not attempt climbing them after seeing people come down.
Bring your guidebook or join a guided tour to learn the history, or for budget travelers, eavesdrop on them. There are no signs explaining any of the ruins. Be prepared for lots of walking, and bring water and bug repellent. Chips, soda in glass bottles, and water vending begins throughout the park around 8am. There are several small restaurants located outside the official entrance, which are possible to walk to and return to the park. People in town act like you will starve to death if you do not buy a box lunch from them to take with you. I arrived around 6am, went for breakfast around 11am, and then returned to explore the site until 2pm. I didn't see everything, but it was a plenty of time. Transportation in the air-conditioned van was $80, and the van will stop at El Remate or anyplace along the road if you are staying outside of Flores.