I think MA is a great location for coasting. My parents live in western MA (the Birkshires) and there is a lot of up and down. The better you get to know the route, the easier it is to coast. I would say anything over 15 sec is worth coasting. Make sure you get used to the braking limitations on an uncrowded road! I've never had any trouble, but could see how it could happen when you are first starting out. If it is a really long hill, you can recharge the vacuum for the brakes without starting the engine by letting out the clutch in 5th and spinning the engine for a couple seconds with the key off.
It is harder to bump start the car gently above 55mph because the rpms are too high. It is almost imperceptable at 25MPH. I have found that when going fast and trying to bumpstart, if you let the clutch out for a brief moment and then put it back in the engine starts without much resistance and then the engine speed can be matched and then clutch let out in 5th. It takes a little practice to get it smooth. I don't always bother turning it off when going this fast, because the aero drag slows the car down so fast.
Great advice. Thanks to everyone. I tried my first engine off coasting today and it was excellent. It's a real rush to realize that your cruising down the road without burning any gas at all where previously you'd been wasting presious resources. A couple observations.
The first time I went for the brakes with the engine off I freaked since they're power brakes.
I echo James' comments about bumping at high speed versus low and I'll try that technique next week.
On some downhill stretches I was unable to maintain speed. I can see that at highway speed (~65mph) aero mods will really help and provide more opportunities.