To me, when you gotta go, you gotta go. 20 times more so for toddlers, who don't think about it till it is, NOW! I had the best results with potty right before we leave the house. As soon as you get to the store, mall, you find the cleanest BR- like for us, it is Nordstrom at Southpoint, or Gap. Potty right away, and then you are good for a little while. Potty at least once an hr. I never took a potty with me, how to clean it once it is dirty, yuck. Wash hands super well. They have done studies that say, toilet seats are not the dirtiest places we go. Use your wipes a lot. Potty training was my most hated time of toddlerhood. I hate going in a public bathroom, and all they seem to want to do at that age, is check them out!
I'm now a gma, and I seem even worse in public restrooms. These little girls will NOT go before we leave home, and WANT to check everything out. Good luck, boys are much easier.