Yeah it depends on the security guy you get, some of them will be nice and let you decide and some will make you park where they want you to. Your best bet is 2 rows of 3 cars parked back to back to maximize your space. That has worked the best for us since we can have a common area in the center of the 6 spots.
Coachella '10, '11, '12 (w2), '13 (w1), '14 (w1) and hopefully every one after
"I was born with music inside me. Music was one of my parts. Like my ribs, my kidneys, my liver, my heart. Like my blood. It was a force already within me when I arrived on the scene. It was a necessity for me-like food or water."
Always parked back to back as well. Never seen any security forcing people to all park in a row ... That doesn't even make sense. They couldn't get the second row of cars into the spaces unless they made people back in, and that would be a total cluster fuck!
What they've always done (at least all the times I've gone) is they send the cars down the middle of the camping row and just alternate which direction they have you park ... So if you're in a group you just automatically end up being back to back. I've never had to ask for it to happen.