THE FLYING DUTCHMAN
Like a typical college town, the area of San Francisco right outside the Academy campus features a large number of businesses that cater towards the young cadets. In that tradition, one of the favorite off-campus places to socialize is a pub/lounge known as "The Flying Dutchman."
The bar sells synthehol drinks, although the bartender may break out some genuine spirits for a special occasion. Patrons can also find sandwiches, snacks and hors d'oeuvres.
SANDRINE'S
Introduced in the VGR episode "The Cloud," another place where a smaller number of cadets frequent to relax and socialize is the bistro "Chez Sandrine," located in Marseilles, France. Sandrine's, though is a good bit more classy and highbrow than "The Dutchman"-- people coming there will be more dressed up, on better behavior, etc.
Patrons are more likely to find real alcohol here, mostly in the form of fine French wines and spirits, but it's certainly not a place where people get drunk (at least not noisily) or rowdy. Familiar folks you'll find here are Ricky, the beautiful lady regular, and the proprietress, Sandrine herself.
OTHER LOCATIONS
Other places where you might find the cadets are various Starfleet and Academy facilities on and near Earth. In general, anywhere on Earth is fair game, as all points are within an hour's shuttle ride from San Francisco.