Hi again Lauren. The last several years we have been in Newport OR we have come back to Mesa thru' Sisters on US 20 to Redmond then US 26 to Idaho (reverse of your question). Love Sisters by the way - there is still (as of last Sept.) a great city owned RV park at the east end, just off the highway. Reasonable price too! If you come west on 26 (my preference)the hill down to Prairie City is your only thoughtful area (but not as bad as I 17 into the Verde Valley. There is a lovely State Park at Mount Vernon- Clyde Holliday S.P. Prineville also has a nice cg at the County fairgrounds. Back to Caldwell - last fall we stayed at a very nice cg just north of the freeway - Ambassador RV. I highly recommend that one.
Hope this helps your planning. Hi to Barbara.
John