I rode there a few times before I got fed up with sand by Plum beach... Main road (used by cars to get to the Aviator's parking) is nice and is probably long enough for 2-3 minutes intervals (at least at my skill level; according to Google Maps it's just over a mile long). If needed, I guess, one can always extend over to one of the adjusting runways - surface there is indeed not in great condition and you need to look ahead, but it's not much worse then some of the roads in the city (I wouldn't go all out on them, but probably would be OK doing SS intervals).