The archaeological site entrance, at the end of the road on the southeast corner of Laguna Cobá, has a parking lot with surrounding eateries and snack stands. Be prepared to walk several kilometers on paths, depending on how much you want to see. If you arrive after 11am, you’ll feel a bit like a sheep in a flock.
A short distance inside, at the Grupo Cobá, there is a concession renting bicycles. These can only be ridden within the site, and are useful if you really want to get around the further reaches; also they’re a great way to catch a breeze and cool off. If the site is crowded, however, it’s probably best to walk. Pedicabs are another popular option for those who are tired or have limited mobility. Bring insect repellent.