It’s Sunday afternoon and Sara Leon and her friends and family are practicing quinceaňera dance moves on an oil-stained parking lot off Echo Park Avenue. The kids practice under the direction of Evelin Munoz, who for $700 provides seven dance classes tailored for quinceaňeras. The name of her company is Flash Dance. This is the fifth class for Sara and company before her quinceaňera on Nov 22. Looking good.