I am going out of the country next week and was wanting to know if I would be able to fly without cellular service or WiFi in the DJI 4 go app ??

Getting the hang of this machine and I absolutely love it !!

Phantom 4 Advanced

Yes you can so long as you have registered your drone with dji all will be fine

I would do a little preemptive scouting to be sure the areas you're interested in are accessible re the vast areas of unlockable and not-unlockable DJI NFZ areas.  What I'm saying is, if you're interested in flying in an unlockable DJI NFZ area, you can self-unlock the area for a 3-day period of your choosing in advance (like before you leave the country), then just be sure the info is uploaded to your Phantom before you go.  Later when the date arrives and you're on location, you can fly, without a wifi or cell connection, because your Phantom has  already been unlocked.  Just be sure you're legal regarding local laws.  Good luck

Hello there. I appreciate your time bringing this query to us. Yes, you may use the DJI Go 4 app even without an internet connection.