CUBIC DEFENSE SYSTEMS Inc. and its former president have pleaded guilty to conspiring to bribe a senior Air Force procurement official and agreed to pay $4.65 million in penalties. Colvin C. "Sam" Wellborn could face up to 15 years in prison and a $500,000 fine. . . . A SNIPER in San Jose, Calif., fired three shots at a Marine Corps recruiter, who escaped unharmed in the second such attack in a week in the San Francisco Bay area.