That would be a wild cucumber (Echinocystis lobata), and a really good picture of it. It’s all over the place on the west coast.

Thank you, Trinian, for shedding some light. “Cucumber” makes me think it’s edible…is it?

A message from Trinian:

Uh, never tried. It doesn’t really look very edible…

Go go Wikipedia to the rescue… Nope, it’s rather toxic and not at all
tasty (http://en.wikipedia.org/wiki/Manroot). Given that, and the fact that
the fruit looks absolutely nothing like a cucumber, I have really no idea
why its called a “wild cucumber.”