I booked as a solo traveler, joining a group of 4. Easy booking experience with prompt communication, despite being solo, which tends to hamper some organized trip plans.
I arrived in Xpujil late the night before and stayed at a local hotel, where I was picked up before 7:30am, and after two stops to pick up the others, off we headed west towards the entrance to the road leading to Calakmul, where we met Roberto. After some short introductions, we started the 60km drive-in, with a stop at the archeological and natural museum, where Roberto explained some of the flora and fauna we might encounter on the way to and at the ruins.
After the drive, we got some refreshments and started making our way on foot into Calakmul. Roberto took the time to explain the origins of Calakmul, the relations it had with neighboring rival Tikal and as far as Teotihuacan as well as Mayan civilization as a whole.
We had the opportunity to climb the tops of the structures and once on top and you've caught your breath, prepare to have it taken away again by the sight of nothing but green surrounding you, and the sound of nothing but the wind. Quite a change from places like Chichen Itza and Teotihuacan where one can be overwhelmed with the number of other visitors and merchants.
Apart from the monkeys, birds, and frogs that we saw (thanks to Roberto's great eye and ears), I counted about 25 people maximum during our stay there.
Water and refreshments (bars, fruit) are provided before you head out on foot but would suggest to bring extra and you'll need it (especially if you climbed all three structures on a clear day!) Also, there are no restrooms within the main complex itself, so plan accordingly. We spent about 4 hours in the ruins and had a great picnic lunch that our driver set up next to the van. We drove back, said goodbye to Roberto, and got back to Xpujil about an hour early (the drive back is a perfect time for a siesta).
Overall, a wonderful experience in a magical place. Plan for a whole day, and especially if you are visiting from Bacalar, plan to spend an evening or get there the night before. I highly recommend Ka'an for this tour even though you can hire a car/guide independently. Shoutout to Roberto, our guide, our driver and the team at Ka'an expeditions for a memorable time touring Calakmul!