91 bus then bike 7.5 miles
Take the 91 From Eugene Station. Keep in mind that on week-
ends the bus makes only two trips on this route: one in the
morning and another in the evening. Stay on the 91 for roughly
4 miles beyond Blue River, at which point begin watching for
a Cougar Reservoir sign on the right. When you see the
sign, signal that you want to get off and you will be dropped at
the intersection of Hwy 126 and Aufderheide Road 19.
travel for a half mile until you hit a fork in the road. At the fork,
turn right toward Cougar Reservoir. After 3.4 miles you will reach
the dam, at which point turn right. Travel another 4.3 miles until
you reach the trailhead for Terwilliger Hot Spring on the right. Hike
about a quarter mile to reach the spring.
http://www.cougar.org/ (Friends of)
There and other hot springs: