The on-again, off-again career of jockey Patrick Valenzuela is on again. Valenzuela, 39, received a conditional license to resume riding from the California Horse Racing Board Dec. 14, and will begin working horses Saturday, Dec. 15, according to his attorney, Don Calabria."We are real pleased, very, very happy, and hope it goes well," Calabria said. "Pat wants his actions to speak for him. He doesn't want to talk about it anymore, he just wants to ride. He's so anxious to get back on a horse. He was born to do it."Valenzuela's license is contingent on his passing random drug tests, which Calabria felt will occur at least twice a week. The rider has undergone such testing twice a week for the past six months, according to the attorney. Valenzuela must also continue his participation in substance-abuse programs provided by the Winner's Foundation, a backstretch organization in Southern California whose purpose is to help workers beat substance-abuse problems. Valenzuela has been set down numerous times for drugs throughout his career. He won the Kentucky Derby aboard Sunday Silence in 1989, and has captured six Breeders' Cup races.Valenzuela hopes to begin riding races when Santa Anita Park opens for its winter/spring meeting Dec. 26. Valenzuela had made a solid comeback in late 1999 from a suspension and various injuries, finishing second to Laffit Pincay Jr. in the Hollywood Park meeting in which Pincay became racing's all-time winningest jockey. But back at Santa Anita early in 2000, Valenzuela admitted to having taken amphetamine, and was suspended. He has recently worked for prominent horse owner Bob Lewis' beverage distributorship, and Lewis wrote a letter to the racing board on behalf of the rider.