Ah, AI … the interactive “wrong answers only” meme.
There is no CityStrides app. The furthest I have gotten is creating this Ideas post - Create a CityStrides app
You can add the website to your home screen, and it will behave like an app. There’s no offline support, though, so it doesn’t address your lack of a data plan.
You could try memorizing your routes, and potentially create simpler routes. I might live in a place where this is easier than in others, though 
I can generally get by with a kind of “go down street a, turn onto street b & finish everything on the left, then return” plan. I also tend not to stress about optimizing/efficiency as much as others do. … That said, I’ve definitely been in positions where I’m just staring in multiple directions wondering wtf and then digging out my phone. 