In our series, Place at the Table, we look at diasporic enclaves around the world through their cuisines—and the people who, in trying to recreate a taste of home, have forged exciting food scenes that invite others in. Philadelphia’s Rittenhouse Square is home to landmarks like a 17th-century park and the Curtis Institute of Music. It’s also home to Tequilas Casa Mexicana, a 40-year-old family-ru...