The San Diego County Fair opens June 12th at the Del Mar Fairgrounds, and the cheapest ticket starts at $18 — the going rate for the single most SoCal-summer thing you will do this year. Jimmy Durante Boulevard leads you in. The smell of funnel cake and sunscreen meets you before the parking lot ends. Del Mar in June means a particular kind of heat that doesn't apologize — the kind that makes the lemonade taste better and turns a crowd of strangers into people all in it together. You walk past livestock barns and end up at a stage where someone is playing to three hundred people like it's …