DIRECTIONS:
Arrive in Pasadena via the 110, and turn right on Del Mar (4th light). Take Del Mar about 2 miles, past Lake (a big intersection), and then turn right on Wilson Ave. Continue on Wilson Ave until the next intersection, which will be San Pasqual. Park, anywhere you want. (It's safe: none of the parking restrictions are in force at that time/day.)
San Pasqual dead-ends into a path on Caltech campus, on the left side of Wilson as you're coming from Del Mar. Walk onto campus and walk further down Wilson (away from Del Mar) on the little path. There will be a wide driveway/drive into Caltech on your left; turn up this, and the building immediately to your left is Kerckhoff. 101 is the room closest to Wilson, on the end; just walk up the steps, the door should be propped open.
If not, knock loudly!!