most of the charters leave from Playa Del Carmen.....this time of year you are looking at solid catches of Dorado and barracuda....outside chances of getting into some White Marlin as well....make sure you take medicine. Very common for windy hot days and rolling 10-20ft waves....it will make you sick. Even if you don't get sea sick....
I would recommend 1/2 day trip if you have kids. Expect $400-600 half day fees, not including tips. My wife and I go every July and we use Captain Ricks. They have great customer service and we always catch fish.
Here's a couple pics of our trip we just got back from
Hope you have a great time!!!!