You're right about September in Mass- in my opinion it is the most beautiful time of the year up there. I spent nearly 5 years living inside the 495 beltway from January, 2006 'till November, 2010. It was my favorite time to be there.
I didn't have a bike then but, I gotta tell ya, I don't remeber going anywhere at any time when there wasn't a lot of traffic. Narrow two lane roads with no shoulders packed with cagers and bicycles no matter whether it was a weekday or weekend gave me pause when I was considering buying a motorcycle. Don't even get me started about driving on 128 or 495. As things turned out, I waited until I moved back south to get another bike.
My hat's off to ya! Enjoy the great weather and be safe.