did you really interact with all the red statues? (also, did u use the one that only appears when there's are certain kind of weather?i think it was rainy weather) also, did you do the one that is hidden in a sandstorm in the south with the default (Stormy?) weather?
also, you may leave and come back, in order to make people talk to you. And i think u need to talk to the girl telling you that you can use chocobo's, too.