It's a bean (eventually)

Slimjim Bean aka Slender Stem Bean Phaseolus filiformis
CORRECTION 9/28/11 This is Tepary Bean (Phaseolus acutifolius var. tenuifolius) 

Here's another neat flower. Tiny - no bigger than a dime - delicate pink, two lobes on the bottom. Look by the dam and in the riparian area. Native peoples used the later beans for food.