While I am not familiar with this club, it can be surprising how affordable they can be. Some are downright cheap as they got started when property values were really low, so have low overhead. If I were looking for a mooring a yacht club would be my first choice. Some even have moorings left from people who left the club but left behind the mooring. I know on the Hudson River there are a couple and they really do have a value added. Nice facilities and a good group to hang with and even racing.Don, you should consider Centerboard Yacht Club. It is certainly more expensive than the public mooring fields but you get access to the club, social activities, a launch and a place to store your dinghy. The public areas pretty much require you to remove your dinghy or pay a high price to store it.
CYC also has the best protected mooring field and a launch that will ferry your across the harbor to Portland if desired.
When I had a public mooring in Portland it was at East end beach mostly for convenience as it was at least 10 minutes closer than SoPo for us. But there is a crime problem there. We had our mooring ball stolen and our boat was hit. Our friend had his dinghy and motor stolen by some kids although he did get them back. Last year his boat was hit by the Duckboat.
Let me know if you are interested in CYC. We used to be members and on the board so I knew a few folks over there I could introduce you to.
Great Wed. night racing there too although you do not need to be a member to join in the fun.