Groom Lake Road leads from Hwy. 375 (between mile marker 34 and 35) west for about 13.8 miles through the desert towards Area 51. It is a well-maintained dirt road, suitable for all cars in decent shape. There are hidden road sensors buried in the ground along the road, to give Area 51 security an early warning of approaching vehicles. And of course you are watched from the surveillance installation on Bald Mountain, and by the Cammo Dudes at the end of GL Road.
When you get to the signs, or quite possibly long before, you will see the Cammo Dudes parked on a nearby hill. They used to drive white Jeep Cherokees, but today they mostly use Chevy pickup trucks. The cammos will be watching you, but unless you trespass the border, they will keep their distance. Trespassers are arrested, handed over to the Lincoln County Sheriff and are subject to hefty fines (if they are lucky!). So be careful, watch out for the signs and for the orange posts, spaced about 50 yards apart, that mark the border. There is no fence. Be extremely careful when hiking in that area not to cross the boundary.
There is a small turnout spot by the signs, on the right side of the road. Please be sure to park off the road. When you take a look around you will see two surveillance cameras watching you from a hill to the left. Do not hike up to the cameras! They are inside the restricted area.
If you get there at the right time you will see the white bus, a commuter bus for Area 51 workers, leave the base around 4.40pm on weekdays. When you see the bus coming, get out of the way and off the road in a hurry. The driver will only brake for aliens.
If you are really lucky you may see one of the Pave Hawk security helicopters. They used to "sandblast" curious tourists by hovering low over their heads, but this clearly illegal procedure is no longer used. Unless you are hiking in an area that makes it difficult to track you from the ground (which we do not recommend near the border), you will only see the chopper do its rounds patrolling Tikaboo Valley, and then return to the base.
You can not see the Guard Shack from the road. It is hidden around a curve, about 0.85 miles down the road. And of course you can not see the Groom Lake Base itself, which is about 15 miles southwest, behind several ridges.
Update 1/1/2010: Between 12/15/09 and 12/30/09 the remaining 9-mile dirt section of Groom Lake Road inside the restricted area between the warning signs and the old cattle fence near the north end of the dry lake bed was paved. Groom Lake Road is now a paved road from Area 51 all the way to the warning signs. The 13.8-mile section outside the restricted area, between the warning signs and Hwy 375, remains a dirt road.
Update 1/1/2016: In late 2015 the warning signs at the Groom Lake Road "gate" have been replaced with new signs. All of the old signs are gone. There are identical new signs on either side of the road now (see below). No more "Deadly Force", but the new signs warn that it is illegal to fly drones in the area. Not a good idea anyway! The line across the road is now clearly marked and the border a few hundred feet on either side of the road is marked with concertina wire. All long overdue upgrades to keep tourists out of trouble. A new mobile, remote-controlled FLIR camera tower, similar to the one that was added at the back gate a while back, now sits next to the road a short way inside the perimeter. FLIR stands for "forward looking infrared", meaning these cameras are designed to see even at night.
Update 10/2019: In September of 2019 a physical gate was installed where the border of the restricted area crosses Groom Lake Road. This was done in preparation for the "Storm Area 51" event which was expected to draw thousands of people. Only a couple dozen ended up showing up but the gate to clearly mark the boundary was long overdue. Whether the gate is open or closed, please do not go past it.