Many San Antonio music fans were caught by surprise when Hemisfair officials earlier this week trumpeted the relaunch of San Antonio’s decades-gone La Semana Alegre music festival. Officials at the downtown park and entertainment development said the new La Semana Alegre at Hemisfair will take place April 25-26 — a two-day event rather than the original Fiesta event’s week-plus blowout. Other than touting a bill “spanning multiple genres,” organizers didn’t share a lineup — even though they offered a “flash sale” of discounted tickets.