I have done this tour twice--once on Song of America and once on VOS. It is a long excursion but well worth it. There is a long walk from where the bus drops you off to the start of the tour in Tulum. It was very hot and I would suggest that you bring bottled water with you on this tour and your hats.
We didn't have much time at Xel Ha. Remember that you are on ships time and not the local time there is a time difference. \
Our tour guide instructed us to be back at the bus at a certain time so that we could catch the ferry and meet back up with our cruise ship.
Five passengers weren't back on time and the guide went looking for them. He was able to located three passengers but we did end up leaving two passengers behind in Xel ha. This was a ship sponsored event.
It was up to the passengers to catch back up with the ship.
Adventure of the Seas (RCCL) 3/10 -Southern Caribbean
Adventure of the Seas (RCCL) 3/07 -Southern Caribbean
Voyager of the Seas (RCCL) 3/03 -Western Caribbean
Monarch of the Seas (RCCL) 3/01 -Southern Caribbean
Song of America (RCCL) 10/90 -Western Caribbean
MTS Jupiter (Epirotiki) 7/84 -Mediterranean