My dad is from Portland, My Great Uncle is in China, and my cousin is in Booth Bay. So I can tell you a little. The absolute best paddling expierence I have ever had was in Booth Bay with my cousin and his dog. Mind you I love Maine, and would there were there work for me.  Water was flat, season was late fall, still some color in the trees, no other boats, just great. First time since I had been in Iraq that I was totally calm and at peace. Water was clear as could be.  Next day weather was pea soup and misreable. Such is coastal Maine.

A lot of places back East pack up after Labor Day.  You may get lucky and score with a local shop, but most places will be getting ready for fall watchers and snow machines/ski season.  As for fishing not sure what trout are doing this late, but I am sure you could wet a fly on some nice water.  Also you may hit it off with waleye, and Small moth bass, and crappie. Bull heads (small catfish are abundant in some waters.   Salt water will be hit or miss.  My Aunt and Uncle (from NV) just got back from Bar Harbor and said the fall colors had not started yet.

Don't be surprised if a lot of locals call you an "immigrant," your not from Maine "dear", upper NH or Upper VT, be prepared. Whine like you are from New York and be prepared to really get the cold shoulder (New Yorkers are generaly dispised for buying up the real estate and screwing up everything). Insult the Patriots, Red Sox, Celtics, and Bruins and expect the same, Down Easter's take their sports seriously.

Take an Orange Vest and Hat with you as most likely it will be Hunting Season for something, and those damn immigrants will shoot anything that moves.

Coastal weather is diferent than as the gulf stream is the opposite of the west coast, you may actually find the water to be warm, but by now stripers and blue fish have headed south. If you get the chance to go after some blue fish though, by all means do it, blue fish are some awesome fish to go after on light tackle.  Its like a 100 pound bill fish in a 5 pound fish.

I hope that helps!