That event looks pretty sweet, its not the one I was thinking of. There might be a few mazdas there, the one in Ohio only had one mazda in the show, I know there are a few rx-7's, miata's, and a couple protege's in Indy. It would be interesting to see whats out there.
As far as what to do and things like that....I live on the far north side of Indy and IRP is on the south side, so I don't get over that way too much, plus there are a lot more mulletts on that side of town, if you know what I mean..... (rlaugh)
I would stay somewhere downtown Indy, there are a bunch of hotels, it would be about 20 - 25 minutes away or so, and there is plenty of stuff to do downtown, bars, museums, malls, resturants, etc. Depending on where you stay, I'm not sure how much you want to spend, but the Hyatt downtown is connected to the mall, lots of bars and stuff within walking distance.