We booked this when we were getting on the bus to the town. The tour was $39 each and that included everything except lunch. The ruins were great and the food in Merida was good too. I recommend this one highly.
We did some shopping in the port shops and then went to Paradise Beach. This was my second trip to Paradise and I was not disappointed. Food at Paradise was great. It is only $3 per person to get into the club. The cab ride was $14 each way. Cabs are plentiful to come back to the ship.