John & Tessa,
IMO, the biggest issue with leaving your boat in any of the
marinas in the
Azores is getting a berth on a floating
dock rather than rafted up on a seawall or hammerhead. The
marinas in Horta and Ponta Delgada are usually very full during the summer months and the only option may be to raft up. Not how I would want to leave my boat.
I believe the best
advice is to try Terceira. I think you will have a better chance of getting a berth in Angra do Heroismo or Pria. I don't know about flights from Terceira, but the worst is you will have to fly to Lisboa and change plans there. I seem to remember that the direct flights from the Azores to North America were always booked several months in advance.
John