Is it safe to persist the device user's data in SQLite on Android after logout?

For example, if I have a messaging app, and I wish to make it so that people can log out and let their friend log on with the same device, is it safe to leave all of the existing messages in the database, as long as the oAuth token gets destroyed in the shared preferences?

I don't want to have to redownload the phone owner's messages each time a new user logs in?

If I was to leave it there, that means the person who borrowed the phone might be able to have their messages read, will it? Or is there a way I can encrypt them on the phone so that even if the sqlite3 db gets compromised, the messages can't be read?

I could make a check box on the login screen maybe that says "this is my phone" and that would allow for persistence on logout?