Having had horses, dogs & goats. There is quite a bit to consider. There are a myriad of options depending on different variables. I would be happy to help you find the right fit. The Portland metro has some great alcoves of horse friendly properties.
It would help to know where you will be working; for example on the east side of town or on the west side. On the west side I would recommend west Beaverton or Hillsboro for acreage and that great country feel. For smaller class sizes, I would pin the area down a little more and also consider the school's overall rating. Let me know if I can show you some properties when you are in town :)
Keller Williams Realty Professionals