I have in recent years become probably overly fanatical, so I have a pretty set exercise regime normally, of which karate is a relatively small part. (Two nights a week at the dojo, swim a mile twice a week, one hour on the elliptical twice a week; plus daily calisthenics and stretching, and a lot of stair climbing during the day at work.) When I travel, depending on where and why, I sometimes back my gi if I know that there will be a place and opportunity to train. If staying at a hotel, I check if there will be a pool or exercise room, and pack accordingly. If nothing else, I have done kata on my own on a beach or in a hotel room, used a chair or stool as a one-step Stairmaster, etc.