DeLeon, who attended both Montgomery County Community College and Temple University, was the best-read columnist for the Philadelphia Inquirer for 23 years before leaving in 1995. He currently writes a column every Monday for the Philadelphia Metro. During his career at the Inquirer, DeLeon was named Best Newspaper Columnist eight times by the readers and editors of Philadelphia Magazine. He also has won Pennsylvania Keystone Press Association honors, and his name appeared on the front cover of the Washington Journalism Review's national 'Best in Business' issue in 1989.

In addition to newspapers, DeLeon has worked in television and radio and has been published online. He has also published two books: America's First Zoostory: 125 Years at the Philadelphia Zoo (1999) and Pennsylvania Curiosities (2001). DeLeon's other writing credits include feature pieces for National Geographic, TV Guide, Sport, Samsung, Philly Sport, Rugby and Philadelphia magazines, as well as op-ed pieces in numerous American newspapers.