Don’t stop believing, but do start planning for traffic delays Friday. San Antonio city officials are warning of potential traffic snarls as more than 35,000 people converge on the Alamodome to see the classic rock act play a package tour with Def Leppard and Steve Miller Band. The concert begins at 6 p.m., which means people will start arriving in the area during rush hour, likely bogging down commuters who pass by the Alamodome on their way home from work.