Before a throng of office workers and scruffy-faced hipsters, Los Angeles Mayor Antonio Villaraigosa on Monday opened Spring Street Park in the heart of the city’s rapidly evolving downtown, telling the crowd that there were more parks to come, including the conversion of a coveted 2-acre parcel across from City Hall. “Not since the late-1940s have you seen the resurgence of downtown, the activity downtown that you see today,” Villaraigosa said.