Hi there,
Have not gone on the site for a while but came across this question and it did not seem anyone had swam with the dolphins last year. I had the pleasure and it was magical.
The one I went on was with a goup that was split up into two and about 6 people per group and two dolphins per group so you have to wait your turn to play with them but its fun watching the others play. I dont want to give the experince away but my partner who swam with dophins in Cancun said the Ixtapa's experience allowed you to have more contact with the dolphins.
I would say absolutley do it.
The only thing that was disappointing was that they are not "free" dolphins that come into a secluded area of the bay to play, rather they are dolphins who were trained at a very young age (I beleive they are rescued) and are always watching their trainer for ques.
-Jennifer