When we were planning our DCL Western trip, I posted the same question here. From what I was told, the dolphin excursions are not worth the money. The posters told me that you spend more time waiting in line and receiving instructions and very little time actually touching/interacting with the dolphins. If anyone has done one recently and this and had a different experience, let us know.
We took a cab to chankanaab national park and enjoyed their beautiful beaches.
They have wonderful snorkeling!