It’s all fun and games until the power line blows up. Foil balloons commonly festooned at celebratory events such as birthdays and graduations inadvertently cause thousands of power outages. The shiny, metallic exterior of the balloons, such as Mylar, are electrically conductive and if they float into and get tangled in power lines, they can spark fires and cause circuits to shut down. New legislation signed by Gov . Gavin Newsom last weekend, sponsored by Assemblymember Bill Quirk, D-Hayward, in collaboration with San Diego Gas & Electric, calls for manufacturers and retail outlets to integra…