Members of rival El Salvadorian gangs were arrested by Border Patrol agents over the weekend just north of Laredo on Interstate 35, an indicator of the increasing through traffic by violent gang members the Laredo Police Department has noticed in recent months."Mostly they're transient," said Sgt. Armando Elizondo, supervisor of LPD's Juvenile Enforcement Team, which deals with local gang activity. "They use this area as a crossing point." Sunday, a 22-year-old gang member was arrested by agents at the Texas Travel Information Center at the 18-mile marker on the interstate at about 2 p.m. He had tattoos showing he's a...