Spywitnesses on the set of “Cadillac Records” in Harrison, N.J., tell us that the diva, who plays Etta James in the flick, ignores kids who wait for hours to get her autograph and instead seems to concentrate on keeping her coif covered. Yes, it was drizzling out, but Knowles ran past cheering fans in a phalanx of bodyguards, all holding umbrellas over her. When she emerged later, she had a blanket over her head, says a source. Meanwhile, the spy adds, co-star Adrien Brody “goes out, talks to the kids, signs autographs and everything.”