If you want to cut over to Monterey from Highway 101, I suggest you take the Highway 156 exit for the Monterey Peninsula. This will put you a few miles north of Monterey and allow you some time for seeing some of Monterey and Carmel's great sights. I would NOT take Carmel Valley Road to get back to Highway 101. First, the traffic through Carmel to get to Carmel Valley Road is heavy and slow and, second, once past Carmel Valley, the road is less traveled and VERY twisty, which will only slow you down. Unless you're already in Carmel, I wouldn't bother.
I suggest you post a question in the Carmel or Monterey forum and ask the locals if they've driven that road and if they recommend it.
Fastest way back to Highway 101, take Highway 68 east to Salinas, turn right on E Blanco Road and continue until you reach the 101 on ramp.
Edited: 1:55 pm, October 12, 2012