Los Angeles AFB Immunizations The clinic is open on a walk in basis Hours of operation: El Segundo 7 a.m. to 3:30 p.m. Monday- Friday Fort Mac Arthur 7 a.m. to noon and 1 to 3:30 p.m. PPD/TB skin testing is not available on Thursdays. Contact information Commercial: 310-653-6607 DSN: 633-6607