…from the producer’s commentary @ IMDb:
The movie was suggested by Dr. Phillips, then Director of the San Diego Museum of Man, to the actor Jeffrey Hunter when they worked together on a project in Central America. It was developed as a documentary, and when completed, it was quite good. However, when we could not sell it, we sold it to a private firm, and they, in order to make it more exciting, an without our O.K. hired prostitutes from Mexico to introduce some wild scenes. These scenes were filmed in Balboa Park in San Diego.