I think you'd be ok camping wild, I've saw evidence of people camping at both Murlough Bay and Whitepark Bay, think as long as you don't light huge fires or anything you'll be ok, I've also saw people camping in front gardens etc so don't be shy in asking, it's a small community here and most people will know somebody that knows somebody if you get my drift. Like others and myself have commented, the coast road on a Sunday is busy, people leave Belfast, drive up the coast to Portrush, have an ice cream and drive back to Belfast again. Any other day of the week you are fine. Stick to the coast road though and don't follow that cycle route 96 or what ever it is, I've no idea who thought it up but it's the worst roads I've ever been on and they've no views or anything, it's basically country lanes not even a farmer would use. Cushendun to Ballycastle via Tor Head is also best avoided unless you like 20% climbs one after the other.