I just got back from a quick two day trip. Whew, I would not think you could do both parks in one day if you want to ride everything, unless you run on battery power. We stayed on site and received FREE fast passes. I cant imagine going without them! But would not pay separately for them, unless I won the lotto. The lines will be long in the summer months, plus it will be sunny and hot! That being said we have so much fun at both parks. If you do go plan it out first, look at the website map and figure out which rides you all must do. My recommendations of must do's are, Mummy, spiderman, jurassic boat ride, and Men in Black. I also love Bluto's barge, its a water ride, like cali river rapids. Only you get Soaked on this one!!! I also love the Dr. Suess theme. Finally, we thought the simpsons ride had a great theme, but the ride itself was just okay. Hope this helps you out some, if you have any more questions just ask.