You do not have to switch your pass if you don't want to. It's completely optional. However, should you choose to change your pass, you can do so between June 3rd and June 19th inside the park at either Cafe La Bamba or the Jurassic Park Discovery Center. After those dates listed, or outside of the hours for those locations, you can pick it up at the Group Sales windows at Islands of Adventure. Universal is trying to keep as many people out of the Guest Services lines for this as possible since those lines can already get fairly long to begin with.