Rick,
I just now used Hwy138 to access Lake Arrowhead to visit some friends. Signs are posted at Summit Valley rd. state: Hwy 138 at Live Oak rd. closed 9-21 through 9-25 . When I got to where Live Oak rd. is there are orange safety fences on both sides of the road and large bulldozers , front end loaders and back hoes parked beside the road. Live Oak road is @ 1 mile west of where Hwy 173 (sorry me ?) starts/stops. So it will be accessible due to this road being closed. If you wanted you could drive through Hesperia via the Arrowhead road route in front of the dam/spillway. Then go to the Bradford ridge :~)
It appears too me that the road dept. is going to take the dipsy doos (small hills) out of the hwy. here. Also they may straighten the road some too. This work appears to be less than a half a mile or less distance.
To be CLEAR : Highway 138 and 173 are open NOW TODAY. BUT are closing from Monday 9-21 until Friday 9-25. That is next week.
Highway 138 and Highway 173 will not be accessible from this route.
Highway 173 is not closed however.
Glad to help !
And I thought you were smater than me !