There's a lot of this plant in this disturbed area and it's all heavily seeded. The seed pods are stickery. The leaves that you see in the picture above are the leaves of the datura growing beneath and around this plant. The photo below shows some of this plant's leaves, though it's the end of the season and they're withered.
Note: More research has suggested this may be epazote. December 15, 2014.
After a bit of sleuthing I believe this is Chenopodium murale, nettle-leaved goose foot, or lambs quarter. According to Plants for a Future, this plant and its seeds are edible, though moderation is cautioned as constituents include oxalic acid and saponins.
Plants for a Future
Chenopodiaceae of California, US, different goose foots in California