No government has built a wall as apparently impenetrable as the cultural rampart that keeps the classical music of Mexico and other Latin American countries out of the U.S. consciousness. In attempting to scale that wall, the Black Pearl Chamber Orchestra began its second season Thursday with Mexican "classics," works by early 20th-century composers whose names, at least, are known. Conductor Jeri Lynne Johnson led what may have been the first local readings of music by Silvestre Revueltas, Manuel Ponce and Jose Pablo Moncayo in a Hispanic Heritage concert at Temple's renovated Baptist Temple.