My concern with the 138 is the strech between the base of Cajon Pass & the turn to Wrightwood. It is very steep. Often very slow trucks & very fast cars. Mostly 2 lane with insufficient passing lanes. As others have said it depends where you are going. We recently, from the Temecula area, used the 71 to access the 210 to head up to Morro Bay. You can access 5 that way. When we are heading to family in Redding, I always go up Cajon Pass, 395 to 58 then to either 5 or 99. To avoid as much traffic as possible, we take the 215 to Newport to 79 to Domenigoni Parkway to Warren Rd to Ramona Expressway to 79 to 10 to the 210 near Redlands. Good route for any size rig.
