Working out is a pretty silly idea, really. With a few smart lifestyle changes, you can get your daily dose of exercise incidentally to whatever happens through the day. Otherwise, you just worry about forgetting or not having the time, etc.
For example, I cycle everywhere. Using the trains and some foresight as to how long it'll take, I can get anywhere I need to be.
lol wat
So you can have massive legs and no upper body strength? If the choice is either cardio or resistance training, you should always choose resistance.