The three largest cities in Palm Beach County are West Palm Beach ( first , 150,000 people ) , Boca Raton ( second , almost 90,000 people ) , and Boynton Beach ( third , almost 70,000 people ) . Boca Raton ( South County ) , is the second largest , having a population approaching 90,000 . Boynton Beach ( South County ) , is the third largest city , with a population nearing 70,000 residents .