The shot of of Sandra in the car yelling at Gerry and Steve, from the boys' point of view, may not have been staged: the runway for Gibraltar Airport really does cross the main road into town. When a plane comes through, arms come down to block the road (similar to a railroad crossing) to stop the pedestrians, bicyclists, and cars from crossing the runway. This arrangement places GIB on many "world's most dangerous airports" lists.
The monkeys on Gibraltar are, in fact, scavengers that will enter hotel rooms and even attack lone or unwary pedestrians. In general, they do not attack humans in the more populated areas, but they will do so on the Rock itself. Visitors to the Top of the Rock are warned at the ticket offices not to bring plastic bags up with them as the monkeys associate plastic bags with food and will attack humans for food. (The monkeys believe they are in a higher social level than humans, and in their society, the lower levels owe food to the upper levels. The monkeys are utterly unafraid of humans.)