OK, we have a problem with foxes here (West Sussex) and they are very bold indeed. They will only stay out of the garden when the dog is actually present and since they are night creatures they can still be a nuisance. The lst suggestion was good some dogs wander all over flower beds etc without a backward glance so you need to know how the dog will behave in the garden and be prepared to PUP as we put it (Pick Up Poo).

Good luck hope the dog helps.