The Peterson Ridge Trail System just outside of Sisters, Oregon, have nice views and an extensive network of easy to intermediate high desert trails. The whole area is relatively flat, with no significant climbs and downhills that require constant pedaling to maintain speed. The best views are along the upper section of the West Peterson Ridge Trail.
The trails get hot and dusty at the height of summer and are popular (though not as crowded as some of the trails near Bend). In the fall the dust gets knocked down by the first rains, and the cool sunny days and lack of other riders make the area feel like your own personal playground. The trail system is well signed, and there are free trail maps available at the main trailhead and from the bike shops and other businesses in town.
For rental bikes and good recommendations on which trails to ride, stop in at Eurosports, where the staff is friendly and knowledgeable. If your bike needs some work, you can sit at their bar and enjoy some local beers on tap while they get you fixed up.