Although Florida hosts great migratory flocks of geriatrics from the Northern territories, they seldom bring their eateries along with them and thus, while the Northeastern USA is saturated with diners and all-night cafes, these low lands have but a handful scattered throughout. And no, I'm not counting the likes of Waffle House, Huddle House, Denny's, and IHOP because apart from the Waffle House, reigning Southern king of filth and convenient biofuel, these places lack character. After all, you wouldn't consider McDonald's when discussing the best place to get a burger in your locality.
The Metro Diner in San Marco gets my Northeastern counterpart's seal of approval when it comes to diners and, being a Jersey girl, she has a lot of standards with which to measure it. Being situated just outside of San Marco Square gains it a few points and adds a slight air of poshness that wouldn't be present if it were located anywhere else within Jacksonville's immense borders. Be fully prepared to wait ten or fifteen minutes before being seated as there is usually a small crowd waiting outside but there is plenty of complimentary coffee to help you jitter through the wait.
Inside they've managed to capture the antique dinginess of Northern diners which, whether intentional or not, adds a bit of authenticity and ensures that your stay will be comfortable but that you won't mull around too long and hold up the crowd outside. The food is also rather tasty. The breakfast burrito and eggs benedict I've sampled on my two visits there were very good, filling, but not overly greasy. The chipped beef is apparently up to the Northern standards as the wife refuses to eat anything else there, being endlessly thrilled with having found somewhere below the Mason-Dixon line that serves chipped beef.
The only downside to the Metro Diner are the hours. Open everyday between 7am and 2:30pm, you won't be stumbling in here after waking up at 4pm or coming back from the bar at 4am but if you're looking for great breakfast food at hours befitting a respectable human being then you'll be just fine.
3302 Hendricks Avenue
Jacksonville, Florida 32207