It depends on the week of course. I was just there Saturday. park opened at 8:00, got there about 8:15. Went on Spiderman first, then walked over to Harry Potter and got right on FJ, no line at all (the sign said 5 minutes). When we got off - it was still at 5 minutes. Walked around the shops, went on the small roller coaster right next to it..........it still was 5 minutes. (probably about 10:00 by now?).
When we walked by again later in the day (say 2:00ish), it said 40 minutes. But every time we looked at one of those signs that lists the wait times, it never was more than 30 minutes.