So I ended up camping for a week outside of Bend, OR and spent three different days looking for Edison Ice Cave. A few excursions later and many more maps, we never did find it, but we did have a very nice offroading experience none the less. Hopefully we'll find it next time!
Me driving, can kind of see the trail out front:
Parked, have to hike in. We are on FS Rd 600 off of highway 45:
This kind of shows the terrain, it's a sandy mix about 3 inches deep with volcanic rock. Not bad though, used to be a gravel road several decades ago, some large rocks but embedded pretty low.: