After more than two decades of working as a prostitute in Mexico City, Esperanza Escobar found salvation in a most unexpected place. She regularly visited a hair salon in the heart of La Merced, the city's tough red light district, where she would take a break from days when she might have as many as 60 clients wanting sex. The hair salon, which treated women like Escobar kindly and keeps them coming back with rock-bottom prices, is in fact a fro…