Spray paint cans are once again rattling at the @HOPEOutdoorGallery. After years of delay, Austin’s landmark graffiti park is reopened on a 17-acre site near the airport. The property is part art park, part cultural events center. It features work from more than 30 artists inside the 6,000-square-foot gallery and on mural walls. There’s also a cafe and shop where one could buy, say, spray paint to tag the gallery’s outer walls. On opening day last month, visitors painted robots, band names, eyeb