If you look closely you’ll see that there was a smaller sign below the “no u-turns” sign that read “Midnight to 6am”. That tells me it was specifically aimed at people who were cruising and repeatedly cycling through the neighborhood late at night. It just happens that the bar in the area at the time was a gay bar, but I suspect similar signs would have also gone up if it was a heterosexual meet market.
Growing up in the Quad Cities it was a popular thing to cruise 23rd Avenue in Moline. Eventually the city put up signs banning “unnecessary repetitive driving,” or something to that effect, because people who lived along the avenue were tired of the late night commotion.
It sounds to me like the people in Silver Lake, Los Angeles, were targeted not because they were gay but because neighbors were tired of the late night commotion.