Mostly, she went outside when we had her out on her leash. When we stopped at a rest area, we walked her.
When we walked around the hotel, my husband had rigged a diaper (she didn't like it too much, but she tolerated it) by cutting a whole in a baby diaper for her tail, but she never actually went in the diaper. We usually have a towel under her in case of an accident when we hold her and we did that when we weren't using the diaper. We wanted to be extra careful since the hotel was being very gracious about letting us take her anywhere except the restaurants (for obvious reasons).
We also have a bag that we carry with all of her stuff in it. We always wipes and paper towels in case she has an accident. Wipes clean up iggy mess off of pretty much any surface without staining.