The Deschutes River Trail is one of my favorite spring rides. We usually do this as an overnight trip from Portland, camping at the Hood River Saddle Club. The trail is only open to horses March through June, aim to go in April or May as March can be pretty cold and June can trend towards too hot, as there is no shade on this converted rail bed trail, but the views and the peacefulness of riding along the river are unmatched. Several restrooms and good grazing meadows along the way (kayaker camping spots). Reservations for horses are required (via Oregon State Parks website) and the trailer parking really only has room for two trailers, three horses or less, but it's worth the hurdles to do this ride annually.