In short: how do you do it?

The frequency at which I travel has begun to rise, and while I've got plenty I could do with ear training and mental practice, there's also the simple fact that muscles do atrophy, and if I'm to work on and maintain my physical technique at all, there's got to be a way to do it.

I've taken to drumming Hanon patterns with my fingertips on the bus window, dinner table, and other random surfaces. I have an ear training book that I'm (very slowly and painfully) working through, and am thinking about one of those "yes, you too can have perfect pitch" training programs (which I've heard... mixed things about, but am willing to try). I could certainly try to spend a few evenings in jazz clubs while I'm on the road, soaking up some listening. I could also bring a portable instrument (for instance, take my guitar along) or try to find pianos where I am.

This seems to boil down to three questions:

  1. How can I improve on the piano without access to any instruments?
  2. How can I access a piano while traveling?
  3. How much would working on another (portable) instrument - likely guitar or bass - help my jazz piano studies?

Any suggestions or leads would be awesome.