There are two "good" places to have sex in a truck stop. The obvious choice is in a truck. This is not private--the movement of the truck's cab is an unmistakable sign that sexual relations are occurring. A better (more discreet) place is in the bathroom. Most truck stops have private bathrooms with showers. Beware that truck stops are rife with unsavory characters like prostitutes, drug dealers, speed freaks and truck drivers (lol). As such, they are also frequented by law enforcement.