Well, I think I lucked out. My dogs have always seem to eventually start going where they didn't play in the yard. They seemed to gravitate away from the play area after about a year and a half in age.
Have you tried to take your pup out on his leash to the area where you want him to go when you know he has to go (ie. after bed time, after meal time) and walk him around there until he goes and treat and praise every time? Treats and praise always seem to get a repetative action.
Good luck!
Louise