I prefer taking the fire road up (which was hard enough for me) but you could also take Sunset trail too if you want singletrack (I'll add a trail for that after I ride it). If you stay on the fire road, keep right at any forks.
Take the second fork which will go to Echo Mountain (there's a sign). At Echo Mountain read some of the history, take in the scenery, and don't forget to try out the echo phone (explore around until you find it).
Now head down the mountain. There's some sharp switchbacks and fun spots. Also, a lot of hikers - avoid the weekend if you can.
The trail ends at Lake so you'll have to ride the street for a short ways back to your car. It's actually kind of pleasant since it's downhill, few cars, and nice breeze. I have to give this ride high marks since it's so easy to get to and there are several options other than the one I listed. I'll be back so I can try out Sunset trail.
Take Lincoln Ave. all the way north, turn right on Loma Alta Dr., left on Chaney Trail, right on Echo Mountain Fire Rd, park.<br /><br />There may be an alternate trail head on Lincoln if you don't want the last leg of the loop to be uphill (scope it out on google maps). I had a friend drop me off at the fire road and then rode home to Pasadena - so I haven't confirmed this yet.
http://www.singletracks.com/item.php?c=1&i=3095