Karen,
Thanks for asking your question to planDisney!
The way that the park hopper option works with Walt Disney World
ticket packages is that you have to purchase it for the entire package. You cannot purchase the park hopper option for just one of your ticket days.
But having that option to hop from one park to another is one I recommend to most of my friends planning their Walt Disney World vacations. It is great to have that choice available to you, if you are just feeling like a change of scenery on one of your days. Of course if you want to park hop you do have to wait until 2 pm to do so, and the park you are going to has to have available space. But I have never been unable to hop from one park to another. It could happen on some of the busier days of the year, like Christmas Day, but otherwise you should be good.
BONUS TIP #1On days where you are at either
EPCOT or
Disney's Hollywood Studios, park hopping between the two using the
Disney Skyliner is a snap! Like with the
monorail connecting EPCOT and the
Magic Kingdom Park, the ride is not just convenient, but an attraction unto itself.
BONUS TIP #2Regardless of where you spend your days, consider using the park hopper option for evening visits to EPCOT for some of the great dining choices. Even just walking around the World Showcase pavilions and grabbing some small bites is a great way to both explore some new flavors and enjoy the park atmosphere.
Write me back if you have any follow-up questions.
Have a Magical Vacation!Doug