You guys crack me up!
Don't visit Alphabet City and Spanish Harlem? LMAO.... I won't even comment on that.
The trains run about every 10 minutes and will be PACKED all day and all night. No they don't look like the trains at the King Kong ride in Universal Studios. They're clean and most are state of the art. Just be weary of your surroundings and don't leave your wallet hanging out... isn't that the same in other cities?
Not bringing a purse is a good idea. You'll feel more comfortable. Wear sneakers and layer up!
Getting a good spot in Times Square for midnight will be hard. If that's what you want, you will definitely have to "secure" your spot well in advance of the ball-drop. It is a wonderful experience but the reality is that, yes, you will freeze your ass off and it will be packed. lol... But you'll never forget it. Don't drink too much. Cops will be everywhere and a summons is their favorite holiday gift.
Tourists will be everywhere. You can spot them easily -- they always look up when walking and have a camera hanging from their neck. lolol...
I live and breathe Manhattan... PM me if you need help.
Have a great time and don't forget the camera!!!