Spending 6 nights in Midtown in Dec. our plans call for frequent use of the subway from Central Park to Madison Square area. When is the subway to late to use? Or should we just walk up one of the main aves.?

In Manhattan in particular, the subway is 'safe' up to at least 1am, and I often ride it later than that.

Where specifically are you starting? Going to MSG? Madison Square Park?

Staying at Hilton Ave of Amer & going to Madison sq Gard, Empire S Building & maybe journey across Brooklyn Bridge.

It's not a bad walk from the Hilton to MSG, about 20 minutes ... cheap cab ride ... or subway.

Do not take a taxi from the Hilton to MSG in Dec. It will take forever.
As Gekko said, the walk from the Hilton to MSG can be enjoyable, especially if you walk down 7th Ave/8th Ave. through Times Square & so on. Beware that the walk will also seem to take forever with the crowds that'll be in Times Sq. If you're in a hurry you can walk down on Ave. of the Americas & cut across to 7th Ave. once you're below 42nd street where the pedestrian traffic reduces significantly vs. Times Sq. Less interesting this way but more effecient.

If you want to take the subway, your best bet is to walk to the subway stop on 53rd & 5th Ave. & take the E train down to Penn Station (MSG is pretty much on top of Penn Station). I take the subway at all times and find it safe but 1:00a.m. may be a good rule of thumb for someone who is not familiar with the system. Another good rule is to always be aware of your surroundings but avoid eye contact... it's an art that NYers learn over time. So, you'll notice that locals tend to look down at their shoes in elevators or in subways look down or generally pretend to read the ads in the subway. It's a bit stranger really.

I would feel comfortable taking the subway through the night provided I was with a group of people. If it makes you feel more comfortable, you can sit in the conductor car on the train. Most of the stations you'll be in have clerk, so you can ask them where to stand in order to find this car. I would also add that if you are going most places in the city late night (even midtown), a cab won't be bad in terms of traffic.

The NYC subway is one of the only systems in the world that is open 24 hours, though trains are noticeably less frequent after midnight. Up until 2am or so, you'll find the subway pretty busy, particularly during the holiday season, when there are a lot of tourists in town. And there are always cabs if you don't feel like doing the train.

I've ridden to subway before in Midtown up to 2AM by myself and have felt perfectly safe.

If it's coming from an 'event' at the garden, it will be loaded with people. If in doubt, take a cab.

We take the subway up until 12 or 1am. And after that we don;t take if not because of safety concersn - but because the trains run much less frequently (you may have to wait 20 minutes) and cabs are easy to get and fast.

never!

Each person feels comfortable at different times. Since you could get lost you may want to use cabs after 9pm. It also helps because some of the trains slow down after rush hour.

My niece had similar concerns, but found that the large number of people exiting the even at MSG was so great that she felt perfectly fine walking back to Grand Central as one big group.