Without getting very scientific at all everyone is different.. it is whatever works best for you. I can't do either, lift or cardio, before 12 pm.. I'm just not a morning person.. It'd be a waste of a workout of I tried ... I get my best pumps between 4 pm -6 pm.. That's just my body's cycle.. I'd try a few different times and do whatever works best for your body & schedule.

If you are primarily interested in burning fat you should do your cardio in a fasted state or after you have depleted most of your glucose levels. Do your cardio before breakfast or after you have lifted weights. In either case you have low glucose levels in your muscles so the primary source of energy will be fat. If you do cardio after you eat or before you lift your muscles are full of glucose and that will be the primary energy source instead of the fat. When doing your cardio in a fasted state, be sure to drink plenty of BCAA's to help prevent catabolism of your muscles.