There are quite a few restaurants of both the fast-food and sit down variety within 15 minutes of the track, all near the I35/Aquarena Springs exit. There is also an AutoZone there, FYI, as well as several gas stations. To my knowledge those are the closest gas stations to the track so top off before you get there.
The clubhouse at H2R is very nice and the back porch makes for a great covered viewing area in between run groups.
As John mentioned, there are some
oil-pan-killing bumps on the approach road (Harris Hill Road) from the south, just before you pull into the track facilities. If you're coming up from that way keep them in mind. I haven't made the trip from the north (Yarrington Road) approach so I don't know about that way.
At any rate I'm sure the H2R owners would appreciate sensible driving arriving and leaving the track, anyhow; people tend to get amped up watching cars turning laps, and I've seen a few smoky burnouts by people leaving the facility. There are residences all around H2R, and in the interest of keeping the peace with those folks (and thereby ensuring Harris Hill is available as a venue for years to come) it would be wise to drive sanely on the approach roads.
John, do you know which direction we'll be running? I personally favor counterclockwise as I think it flows better, but lately it seems that everyone runs clockwise. Either way it's a very fun track, with a nice combination of corners and a couple of sections that will separate the men from the boys. As someone mentioned, runoff areas are not the greatest. I've seen cars come in with cockpits full of weeds, full of rocks, or full of mud, depending on where they went off and what the recent weather had been like. With the rain that the area's getting today it wouldn't surprise me if there is some water across a couple of parts of the track. Hopefully all of the fat tires will squeegee those dry in a hurry.