My knowledge of the foreign community in Hokkaido leads me to think that there would be more than ample opportunity for you to fall back on English. Not having actually ever been up there, I can`t say anything reliably or from personal experience... But it does seem that there is a large and active expat community. Not to mention that Hokkaido tends to list pretty high on the "where I want to live in Japan" list foreign teachers and students come up with.
Gifu is a fairly nice place. Not a large foreign community - and certainly not a popular place - but very convenient and a great hopping off point for visiting pretty much anywhere else in Japan. It can be very hot, or pretty cool - just depends on where in the prefecture you live. As far as living costs go,
you can indeed get a one room tiny apartment for that type of rent.