There are three things you can not make a toddler do, eat, sleep and be potty trained. (sigh) Otherwise you are trained to leap up every so often and ask, "Do you have to go to the bathroom?" (double sigh)
I speak from experience. My friend and I took our sons and my daughter on a short trip to Canada. My daughter decided to be potty trained on a 4 day trip to Victoria-Vancouver. We took the Princess Maugarite--ferry, and train. We visited every!!! bathroom on ship, ferry, bus, and train, hotel, restaurant...no matter what they looked or smelled like. And she decided she didn't want to go poops on top of that. But of course every time she ate her body betrayed her. She refused to wear diapers but we didn't have undies with us....
Good thing the trip was only four days long. I was so glad to see my husband.
The example being you never know when it is going to happen. And my daughter was truly "trained" after that trip.