If it is suitable for outside growing then yes, you could plunge the whole pot into the ground. However, the rhodo will quickly become pot-bound (it possibly is already) and suffer because it cannot get enough nutrient and moisture. If you are prepared to bury the pot then I would either smash the pot (clay) or cut it off (plastic). You will need to spend some time to loosen the roots as they will be tightly bound together.

I agree bulbaholic. if you are going to bury it get some one to help lift it into a table/wall and cut it off.