The Getty View Trailhead is on Sepulveda Blvd on the south side of the Sepulveda Pass. Here is a link to a map showing where the trailhead is: http://www.lamountains.com/maps/gettyview.pdf

The trail basically winds around a bit and goes up to a fire road. On you way up the winds you get a great view of the 405 freeway (just what you want), in the lower elevation of the trail I inhaled a good amount of car exhaust (you can look at the pictures and see how close to the freeway the trail runs). The trail isn't that long.

I mountain biked this train but I wouldn't recommend it, the trail is very narrow and there are several switch backs that are sharp enough to make riding the trail difficult for all but the most experience rider. Riding down was pretty fun but you don't want to forget the switch backs and go flying off the trail. The other thing about riding this trail is that it isn't maintained for riders - it is maintained for hiking and is very narrow. All in all, there are trails around that are much more fun to mountain bike on than this one.

As for hiking or train running, if you are looking for something quick, check this one out. The trail up to the fire road is only about a 1/2 a mile long. One of the guys that I talked to about the trail said that he stops and trail runs the trail each day.

When I was there I only saw 2 people on the trail and I used to commute by the trailhead twice a day and it didn't ever look packed.