Wow, that was fantastic! Top marks!
I think we all guessed the general gist that they'd be trapped back in time by the Angels, but I didn't see anyone guess the specific mechanism of the time distortions preventing the Doctor from landing in that time zone. Although, once he had a tough time initially, it was pretty obviously the reason.
There are a couple of obvious ways of retrieving Amy and Rory though. For one thing, they lived to be over 80 years old. They'd naturally age out of the restricted zone of NYC in the 30s. Shoot, they'd live until 1980 at least!
Or, he could go to that time zone, visit a planet with FTL technology and then pilot the ship to NYC of the 30s. Pick them up and fly back to his TARDIS. It sounded like only that specific location and time was off limits.
Problems aside, I enjoyed it! It was a great way to send of Amy and Rory.