Althogh the official opening time for most parks is 9am, the gates sometimes go up up to 30 minutes earlier on busy days. So, it is worth being at Universal by 8:30am if you can, but bear in mind the traffic at rush hour. Seeing that you have properly recerved full days for IoA and Universal Studios, being there by 9am is more than sufficient to see everything as long as you are clever with use of the UE passes.

Two tips: Don't miss the great Beetlejuice's Graveyard Revue at Universal Studios. Then, when you do IoA, go anti-clockwise, starting at Suess Landing and arriving at Marvel Super-Hero Island last. That works out much better because (among other things) you arrive at Duelling Dragons earlier in the day and that has potentially the longest wait if you miss out UEs.