Welcome to the Gayborhood: In the first study of its kind, the real estate website Trulia has identified the zip codes with the highest concentration of gay couples (sorry, singles). Using data from the 2010 census, the study found that 14.2 percent of gay male couples make up the population of 94114 (Castro in San Fran), while lesbian couples make up 5.1 percent of 02657 (Provincetown, Massachusetts).