Klamath Falls has some mountain bike trails in town that while maybe not worth driving all day for but, if you happen to be passing through town they are definitely worth stopping for. There is a trail head a little less than a half mile from Highway 97 with trail info at a kiosk there. From the south end of town you take West Main Street under 97 which becomes North Carroll Street. Make a right on Cypress Ave and the trail head is about a tenth of a mile on the right. The GPS coordinate for that is 42.219838, -121.796467 Hutches bike downtown has maps to give out if you need one to carry with you. Or you can print the color ORMTB one made with GPS data sent in buy local riders.
The trail riding is very similar to Horse Ridge east of Bend if you have ridden that. Most of the trails are single track and there are enough of them you can ride for an hour or two. There are views of town and Klamath Lake. It is right on the edge of the transition from Ponderosa to Juniper forest with the common Oregon desert brush species. The climbing is not too steep and there are enough rocks here and there to spice it up a bit.
Many of the locals also ride the excellent Brown Mountain loop which is about 35 miles northwest of Klamath Falls on highway 140.
In addition to mountain biking there are lots of good paved low traffic back country roads in this part of the state. The big commercial bike tours frequently run their tours in and out of Klamath Falls.
Here is a free printable 8.5 x 11 color map of the trails near town. In the map below if you click on the Earth tab you
can view it in 3D if you tip it using the controls on the left side that
will appear once you click that tab.
If you want to check it out in Google Earth here is a file for that.You need to have the free desktop version of Google Earth installed to view this file.