I just listened to a radio interview that was done a few days ago with Andy and Tessa by phone from Hawaii. Great interview. you can find it in another thread on this board.
I personally think that Andy knew early on the women he was looking for and was hoping she would have the same feelings. He stated at least twice that if Tessa was leaving it was all over for him. Also that if her family didn't accept him it was all over for him.