Arroyo Seco Boulders Climbing

The closest city is Altadena. From the 210 near La Canada and Pasadena exit Arroyo Blvd/Windsor Ave, head north towards the mountains. Go about one mile and park on the left in the small lot just before the gate and where the road turns right. (Right by JPL). This is a popular parking lot for hikers and mountain bikers and you do not need an Adventure Pass.

For the Bridge Boulder and Wall Boulder:

From the parking lot after about a mile of walking the asphalt turns to dirt and splits into a Y near some buildings. Stay to the left. Hike another 1/4 mile to the wall boulder, on the right or hike another 1/4 mile past that and cross over the second bridge and go down to the boulder about 10 feet on the left. (Edit 9/2018: As you are crossing the bridge, look down left and you'll see it, make a hard left down at the end of the bridge) 

For the Canyon Crest Boulder (You can approach this 2 ways):

From the JPL parking lot walk 3/4 of a mile, then turn right up the first stream. Then hike about another 1/2 mile, crossing the stream several times and then you’ll see the boulder on the left side.

Or the lazy way, exit the 210 at Windsor. Turn right on Woodbury, left up Lincoln, then turn left on Canyon Crest. Go about 1/2 a mile and park in a small turn out on the left or right. Then walk down into the canyon and downstream and you’ll see the boulder.