If you are going to fish the Millers River then I would recommend buying the guide available on this Blog :
http://millersriverflyfishingforum.blogspot.com/2011/01/january-doldrums-things-to-do.html
Mass. ( Eastern Mass.) in general is not the best for trout fly fishing rivers and streams IMO unless you want to hike out to the Millers, Swift or Deerfield. That's why I switched over to Bass fishing last summer. There is the Assabet in Concord - but that gets heavy pressure.
Mass Wildlife does do a great job stocking ponds with Rainbows - but just not the same as seeing your dry fly float down into a river pool. Check out their site for a list of stocked ponds.
But if you want to be able to just drop down the street for fishing, then you gotta switch over to Bass fishing from Trout.