I think this is subject to opinion really bayside...
If you've been before and don't intend on going on many rides then probably not.
However, if you haven't been before and want to try and do ALL the rides then, peak season in July? probably a must.
The bigger and newer rides will be 90 mins - 120 mins wait in line (in 90 degree + heat to boot).
I take it you're aware that there are TWO Universal parks? Studios and Island of adventure. You will be pushed to do each park in a single day (each park = 1 day = 2 days total) You could lose half a day just stopping and looking in 'Citywalk' on the way to the park entrances as well.
Have you checked out the 'flexticket'? I think there's a version of it that gives two or three fast track entrances as part of the purchase price.
Mark.