I have asked many times over the past few years and have always been told its ok to take the towels from the resort to the water parks
but...
They prefer you to take the towels from the pool not the room,
They prefer you to return them to the return area at the pool rather than leave them in your room.
and...
They prefer you return them to the resort and not leave them at the water park.
Apparently the room towels and the pool towels are washed separately to deal with the chemicals.
TJ