We've had to wait up to 30 minutes to be seated at Sci Fi, with the exception of the time our ADR was at 11:00 when it opened. That time we were seated almost immediately.
The good thing is that once you're seated, service is usually pretty quick. Last trip was when we had the 11:00 ADR, and we walked into the 12:00 noon Indy at 12:02. It was standing room only, but we made it. It was a spontaneous thing that just worked out.
If your ADR is at 11:30 and the show is at 1:15, I think you'll probably be okay. Hopefully they won't be too backed up that early in the lunch schedule, and you'll be seated fairly quickly. I'd be there to check in right at 11:15. We made it in just over an hour, and you will have an hour and 45 minutes.