FRESNO, Calif. (AP) -- In a trailer park tucked among irrigated orchards that help make Californiaamp;apos;s San Joaquin Valley the richest farm region in the world, 16-year-old Giselle Alvarez, one of the few English-speakers in the community of farmworkers, puzzles over the notices posted on front doors: Thereamp;apos;s a danger in their drinking water....