Andy,
Holyoke (pronounced by the locals as Whole-Yoke) can be quite dangerous in the canal section - The Flats. Even though the police chief has made some good strides in taming crime, that section still is rather iffy.
Shoot during the day and I would suggest a second photographer to work with.
And yes there are plenty of photographic opportunities in the old mill sections there in and around the canals. The blocks from just north of the VB Hall and south to I-395, between Main and High Streets are great photographically.
When are you going to be actually shooting? I am temporally (I hope) unemployed and do have a little free time - e-mail me.
And Shesh - a New England get together is a good idea. Saturdays is the best bet for me. I am part of the Valley Photo Center here in Springfield. We could meet here or another more centrally located spot. Keep in touch.
gene
PS - I almost forgot about the real name of Webster Lake.