The story is loosely based on the movie of the same name, but you don't need to have seen it (or remember it!) to complete the game. This is an easy Wherigo cartridge, designed with first-time Wherigo players in mind. Just follow the instructions!
The cache is not hidden at the coordinates provided. You will need to download the Wherigo
E.T. Phone Home
and load it onto a compatible device which will guide you along the route. If you haven't done this before a good source of info is What is Wherigo? on the Groundspeak forum.
The walk is about 1km and will take about 1 hour. Areas of the park are muddy and overgrown, so wear long pants and suitable closed shoes. Be aware of muggles, who often sleep or congregate in the park. Not suitable for night caching.