Oh, you love cardio. I know it. But my program, for the most part, makes straight cardio exercise obsolete. The kind of resistance training I recommend includes cardio intervals and compound movements, which effectively raise your heart rate while burning fat. But as I always say, cardio is weight-loss extra credit — it's a great way to get a workout on days when you're giving your muscles a break from strength training. That's why it's important to get a few cardio basics under your belt, so that you know when to do cardio in relation to your resistance training.
If you plan on doing cardio on the same day as your resistance training, it's better to do it after your weight routine. While it's true that a 5-minute cardio warm-up is necessary before any resistance training, doing intense cardio beforehand will deplete most of your available blood sugar, which you need for those quick bursts of energy that resistance training requires. Also, cardio will fatigue your muscles before you lift a single weight, which will prevent you from maxing out your muscles' potential. On the days when you are resting your muscles and doing cardio alone, the best time of day is absolutely any time. The most important thing is that you do it.