Follow-up in case anyone is interested in the process:
We got there at 12:20 (our apt. was at 12:30). First we walked in and stood in a line to determine whether we had pre-registered or not. I had done so, but I didn't have our "tickets" (pre-registration question form) printed out, which slowed our process down a bit. We were shown to another line to get it printed out. Once printed we went to a screening line where we were asked if we were feeling sick, and if we had eaten. In that area we were also given the vaccination flyer (what the vaccination was for, side-effects, etc.) From there we went to a line to get our shots. The shot process was very quick. The only slow down there was that when asked if we wanted a vaccination record I said yes, and she filled it out for us. 20 minutes all told.
I'm impressed by how efficiently this was being handled, there were a ton of people there. If I hadn't pre-registered we might have had a longer wait, but I doubt it.