Yes you can! Just be sure that you are properly signed in to your PRO account on your device before going offline.

Also, you'll need to make sure the campground database is downloaded and the maps you need are downloaded to your device or you won't be able to find what you need once you are out of your service zone. In order to download a map for your road trip from the app, open the specific trip you'd like to download. Tap the 3 dots in the top right corner of the screen and select "Download Trip Maps". From there, you can make sure each segment of map along your route is downloaded prior to your trip.