The first of the switchbacks in the lower steep part
After you passed Montebello School the road becomes single lane
Montebello Rd starts at Stevens Canyon Rd, right by the reservoir. And there's no doubt that this is a tough climb. The road immediately starts pretty steep: 10% and more for the first 2 km. By the time you reach Montebello School the worst is behind you. But you keep climbing for quite some time, mostly around 5% with some short 7% - 8% sections.
At the top you hit a gate which you can bypass. For the next kilometer or so the pavement becomes pretty bad and the remaining 6-7 kilometers to Pagemill Rd are gravel. It's probably ridable on a road bike but better on a cyclocross bike - that's what I did.
The first of the switchbacks in the lower steep part
After you passed Montebello School the road becomes single lane
View to the South
View to the North
The gate at the top
The fog rolls in