Originally Posted by bigredmechanism
Unfortunately, there isn't much going on near the stadium. It's not really walking-distance from anywhere that you might have fun at. Luckily for you, public transportation in NYC is great. Subway from midtown Manhattan (7 Train) will probably take about 25 minutes and cost about 3 bucks each way. If you don't mind spending a few extra bucks (maybe 5 at most) I would recommend taking the Long Island Rail Road. Saves you some time, since there are less stops, and they allow beers on the train as well. Both train lines have a stop directly at the Stadium, so convenience won't be a problem.
What place to stay really comes down to how much you want to spend. Staying at a hotel in Manhattan could get pretty pricy, but at the same time staying at a hotel in Queens (where Citi Field is) is probably not what you are looking for. I'd shop around, and see what you think is best for your needs and budget. Keep in mind that NJ might be worth your while if you don't mind taking a short train ride under the river to NY. Hoboken might be your best bet.
As far as bars and nightlife, there is really tons of stuff to do all around the city. I'm not too familiar with the area near the stadium, but it's really no big deal to take a train back into Manhattan and find a nice place to eat and drink.
I mostly agree with this. I would not stay near the field as it's far out and not the best of neighborhoods after dark. There's not much else out there. The only thing I disagree with is the Hoboken suggestion. Hoboken is a trek from Citi Field. You're probably looking at 2 hours each way. I would advise against Jersey if you can.
There are also some really nice hotels in Queens off the 7 train at Queensboro Plaza that are probably a little cheaper than the hotels in Midtown, but just a few stops away. The 7 train goes right into Times Square as well.
There aren't a lot of great restaurants/bars around the stadium in my opinion. You're better off in the city. I can give you some food/bar restaurants in the city if you tell me what kind of food/bars you're looking for.