You can meet red dots there that give you 2,000 AP a piece.
Three Movers will net you 2300 AP, which isn't all that much. Still the best place to get 'em though.
A suggestion I have is, if you want to grow Materia, put 'em in a Triple growth weapon, such as the Rune Blade. They'll go up like crazy.

There's also the cactuar island, although I can't remember if they net you god AP or not. You probably can't get there right now, though.