More info here: http://www.dot.ca.gov/dist05/paffairs/monterey/mar2011hurricane_pt.pdf
Here's the detour: Southbound: In Carmel on CA 1, turn left (east) at Carmel Valley Road for about 40 miles. At Arroyo Seco Rd. if you turn right and go about 5 miles west, there's an NFS Campground at Arroyo Seco. Great place to stay and have a shower, but crowded on the weekends. Otherwise turn left (east) on Arroyo Seco Rd.. At Elm Ave. veer right, crossing the creek on the bridge. At Central, turn right headed south. after ~5 miles, turn right on to the shoulder of southbound 101, headed to King City (no other road available). Just before crossing the bridge over the Salinas river to King City, exit at Jolon Rd. (aka county rd G14). Follow Jolon (pronounced Hoe-lawn) about 16 miles or so to Ft. Hunter-Liggett. Turn right into the camp (Mission Rd.) - you will need a valid ID to enter the base. Just inside the checkpoint, if you turn left at the next road there is a campground you can stay at. Otherwise continue on Mission Rd. to the left turn at Nacimiento-Ferguson Rd.. Shortly you will reach a river crossing. It's an Army metal grate bridge, ridable but be careful. You can also wade across the river but with this year's rainfall it would probably not be too wise. Continue on N-F rd about 25 miles to the coast. It may seem a short distance but it requires crossing the coast range at about a pass of about 2800'. The descent to the coast is wicked steep. Do take your time and enjoy the scenery, it is one of the most spectacular on the coast. At the coast the road dumps you right at Kirk Creek, a worthy destination.
Southbound, the grades aren't too bad and heading west the climb over N-F is reasonable, but steady 6%+. If you're northbound N-F is very steep as you gain 2800' in 7 miles. There are several pitches in excess of 10%. Similarly the climb from Arroyo Seco on Carmel Valley road is steep but not as bad.
Regardless of what you think of the military ownership of Hunter-Liggett you will find vast expanses of open range, wildflowers and wildlife. It is an extraordinarily peaceful ride from Mission Rd. to the base of the climb unsullied by cattle grazing (unless the Army is doing live fire exercises . . . ). Unfortunately, the roads are regularly patrolled and they don't take kindly to straying off the road nor to dilly-dallying. Best to keep a good casual pace. I've been hassled for taking photos, even in areas where all you can see is vegetation. Be mindful if you ride through this area, as least until you pass the western checkpoint.
Camping: Arroyo Seco NF, the campground at Hunter Liggett, and then there are two primitive NFS sites along NF outside the base, but before you hit the climb.
Supplies: stock up in Carmel Valley Village. Stock up in King City before you head out Jolon. Very limited services between King City and Kirk Creek. Of course there are no stores at Kirk Creek area.
Worthy side trips: Mission San Antonio, on the base. Cone Peak (+5k AMSL), some 5-6 miles north on the ridge road.
I've ridden this several times in the last 15 years, it is spectacular country and even better with a road closure.