The roots of Inverness resident Laura Alderdice’s new children’s book reach back to Puerto Vallarta, circa 1970. Ms. Alderdice was living on the roof of the home of Roberto Perez-Rubio, an artist she met while working at Berkeley Arts. In the afternoons, she learned the language with Mr. Perez-Rubio’s children, Elga and Erika, and played folk music; in the mornings, she took her Sunfish, a small sailing dinghy, out in the Bahía de Banderas, hoping…