IIRC the law in AZ is that the adverse possession has to be 'notorious', or in plain sight. It's up to the property owner to notice.
The owner must know, the owner must have been against you doing it and you must have been doing it for a set length of time.
Know a case where a son tried to claim the family home because he was living there with his mother prior to her death. The owner (his mother) knew he was there but was fine with him being there so he failed the hostile requirement.