I ended up going into Gillespie. It was only about 25 minutes driving time to the convention center, and fuel was $5/gallon cheaper! Sure, Signature would have waived some fees to bring it down to only being $3/gallon cheaper, but still... there is a certain point where I just can't take it any more.
Anyway, I can't say enough good things about High Performance Aircraft in Gillespie! Great service, great prices, they even put the airplane in the hangar overnight without charging me. Their ramp is pretty small, so I would definitely call them in advance if you plan to go there.
I would also take some time briefing the approaches into Gillespie. It was so-so when I went in there, but enough that I needed to shoot the LOC-D. There is a good reason why it's not a straight-in approach-- if you don't see the runway quite a bit back on the approach, you won't be landing straight in. If you brief it and take some time to look at it while at cruise or something, it's fine, but just keep in mind that there is a lot of terrain around that airport-- including some on final! I might think twice about going there at night, unless I started going there a lot.