In the first film, four 16-year-old friends discover a charmed pair of blue jeans that defy the physics of denim: “It makes every one of our butts look good,” marveled one in 2005. Both films are based on books by Ann Brashares, who has so far penned four summers of adventures in growing up. America Ferrera returns as Carmen, the film’s narrator who poses the dilemma for her “sisters”: “how to become ourselves without losing each other.” At the Yale School of Drama, she morphs from a backstage techie to leading lady in the arms of a charming Brit. Tibby (Amber Tamblyn) was an aspiring documentary-maker working at a Wal-Mart type store; now she dawdles on a script for a NYU class on romantic comedy while working at a video store. Last seen at soccer camp in Mexico, Bridget (Blake Lively) from Brown University turns up at an archaeological dig in Turkey. Lena (Alexis Bledel) takes a life-drawing class at the Rhode Island School of Design, then discovers her totally fave Greek is headed for the London School of Economics. Two older women—Shohreh Aghdashloo and Blythe Danner—supply wisdom. Two tawny lads bare their torsos, but the film’s sex is chastely cautionary. Screenwriter Elizabeth Chandler and director Sanaa Hamri (“Something New,” 2006) carry over the clean, bright look of the first film. This esteem-themed romance is aimed at high-school girls keen on getting into Eastern seaboard colleges where they might meet hot boys. With Rachel Nichols, Tom Wisdom, Rachel Ticotin, Leonardo Nam, Michael Rady, Maria Konstadarou and Ernie Lively. 117m. (Bill Stamets)