Usually this question is focused on dogs. Sheep are grazers so they might try and eat some especially if they are young. I don't know if sheep are poisoned by hops like dogs. Some cheap fencing might be a good investment. Maybe someone with sheep can help out more.
my in-laws raise sheep, and based on my observations i'd get a fence up asap. sheep are only a step removed from goats in terms of eating anything they come across.
i haven't heard about their like/dislike of hops, but i wouldn't chance it.