Alondra Diaz can’t get enough of Elmo and Barney, and she adores picture books.  The 14-year-old, who will enter high school next week, has several complex and debilitating medical conditions, including epilepsy, microcephaly and a mitochondrial disorder. Her long-standing team of doctors — a neurologist, geneticist, orthopedist, pediatrician and others — is primarily based at Cedars-Sinai Medical Center in Los Angeles, where Diaz lives.