What do you mean by northern Japan? Northern Honshu or Hokkaido?
Northern Japan (Tohoku)
also has a very distinct dialect that's different from standard Japanese
. Unless you're talking about Hokkaido - most of the people there do speak standard Japanese.
Where you move is going to be limited to where you get employed at.
Both of you need to get a job (and a visa of course). You might be hard pressed to find a decent job as a semi-fluent gaijin in some of the less 'international' areas of Japan, although teaching English would be your best bet.
The only city I've been to in northern Japan is Sendai - it's a very beautiful place, and certainly a decent-sized city.