Road Warrior
I can relate. For the past 6 years I have been a 100,000 mile plus flyer so I have been on the road a lot.
Fortunately I was almost always able to make my own travel arrangements and I would normally have a rental car. That way I could find a gym and have transportation. There are a few hotels with really good gyms, but not very many. For example if you go to LA and stay at the airport Hilton they have a 24 hr Fitness on property so that is very convenient. In Vegas Bally's has a decent health club on-site as does the Flamingo Hilton, but the Golds gyms in Vegas are impressive if you can get to them.
Since I belong to Golds most cities that I traveled to had Golds gyms, but not all. I can tell you that I often felt ripped off when I would be charged 10, 15 or even $20 bucks for a daily pass at a different club, but I would pay it. Sometimes they have a three day or a weekly pass available for less per day. Some hotels have an arrangement with a local health club where guests get in free. Call and ask in advance so you know.
When I could not find a Gym or when my schedule was too busy I'd find time for a run or cardio session. The bigger challenge is to keep your diet when on the road. I have one bag for clothes and the other for gym stuff and food - lol I'm always waiting for TSA to give me a hassle about all of the powders and pills that I bring along - but they haven't so far.
You get extra credit in my book if you can stick with your work out and diet when on the road! It definately takes some extra planning and commitment, but it is worth it.
I have no magic advise other than plan ahead and make the time to fit it in even if it means getting up early. In the end you will feel good about your efforts.