As a kid, I never even knew about it. I knew that 20th April was my birthday, 21st April was the Queen's birthday and 22nd April was my mum's birthday but I never knew that there was any special significance to the next day in the sequence. Even when I later learned that 23rd April is William Shakespeare's birthday, I still didn't know that it was St George's Day. (I vaguely remember asking my mum why there was a white flag, with a red cross, flying on a church, and she probably mentioned St George, but I still didn't associate the saint with any particular day).
Even later in life, St George's Day has never meant much to me. However I had a friend who lived in Ipswich, but whose work later took him to London, who always celebrated St George's Day in style. For example, he decided to travel from London to Ipswich to do an all-day pub crawl around some of his old haunts in the town. He didn't just hop on a train though; he hired a coach to bring thirty of his work colleagues with him and have one hell of a party!