It's being built across the road from (what I presume) is the east side of the park, where New Orleans Square/Frontierland are (if I'm reading the map right). So while not directly next to a park, it wouldn't be difficult for them to build a walkway if they chose to do so. Of course, that's pure speculation on my part.
They could also offer something like "Stay here, get early entrance to Disneyland", if a separate entrance is unfeasible.