Depends how windy it is, if there's no wind go for it. Any wind at all, I'd not... You don't want to fly somewhere where you'll not be able to retrieve the drone safely if it crashes
as it can only fly for 30 m height, you can't take the shot of the whole mountains with it tho. So, consider the wind. in mountains, sometimes the wind is moving so fast. it can be pretty dangerous if your Tello drift away or crash.