The app should support offline editing of documents, spreadsheets and sync them back to Google Docs.
You can go to www.docs.google.com and upgrade your account to a Google Drive account (I believe you can also do this from www.drive.google.com). Google has an iOS app for their Drive service (just search the app store for “google drive”. You get 5gb of free space for uploaded stuff, and docs created in google docs/drive do not count towards the 5gb. The iOS app has an offline storage option for files, as well as support for folders and starring and sharing