No more DATA use from your carrier. All co-Pilot needs is the GPS turned on. You can turn off Wifi and Data and it will still navigate for you.
Also, there is another app that is really great for what you want, it is called WAZE.
Waze is a user defined mapping database that incorporates Detours around road hazards automatically changing your route to handle detours.
BUT, Waze has a decided drawback because it uses a LOT of data from your data plan. It is constantly downloading the next map page in the direction you are traveling. However, if you are trying to navigate through a strange metro area, it is worth every cent that it costs for that trip.
I use it when I need it. Otherwise, I use Co-Pilot