Here it is...trip report where toward the end we went from miter basin directly to USL and then Langley.

http://www.whitneyzone.com/wz/ubbthreads.php/topics/27459/Mt_Langley_Miter_Basin_with_ph#Post27459

Note the sandy wash depicted in Day 5. That's your easy route down from Langley (stay to the south side of the wash if you like use trails).