Numerous counter-demonstrations would occur in response to the Cuban-American "Keep Elian here" demonstrations. At the counter-demonstrations, Confederate flags often made a chilling appearance (especially for the African-Americans who were there). However, few counter-demonstrators ever confronted the Cuban-Americans directly. Some preferred to make their response in the skies, hiring planes to overfly the demonstrators with messages "to love it or leave it," echoing a reactionary invective from the 1960s.
As for this stop sign, it may have simply been a good place to put a pro-"Elian" sticker, although it seems to me a counter-demonstrator may have left it there as a subtle way of expressing a different sentiment altogether.