Oops, they did it again. Here we are, on the eve of the US semiquincentennial, and LA officials continue to load expenses and uncertainty on a Fourth of July parade in the San Fernando Valley. Last month, Mayor Karen Bass’ office balked at covering the cost of traffic control and street closures for the parade –– for the first time in the event’s more than 50-year history. Now, the city might tack on $5K for “no parking” signs along with other sundry expenses.  How much, exactly? No one knows.