I am not sure there is a specific "place" where they drove jet cars, but the reader does learn that driving jet cars extremely fast is a common stress reliever for their society. Early on in the novel, Clarisse describes that many of her classmates had been killed in car accidents due to reckless driving. Also, Mildred even tells Montag he should take the car out for a spin in the country. Mildred adds that she often goes out late at night herself, when she cannot sleep, just to drive, because it's fun. She drives so fast and recklessly, however, that she has hit rabbits and dogs. This too is fun for her; Mildred shows no remorse.