Hi dmcanet,
This is a good question. The answer is simple. There is no right or wrong time to work out. The best time for you to work out is when you: a) have the time and b) feel optimal working out. Some people are morning people and find that they have the most energy and drive in the am, while others need the extra best later in the day. The time that you can give it your all and feel good doing it is the best time for you. The only draw back to working out right before bed is that it may keep you awake longer than you like - this is because increased energy is a byproduct of the workout.
The important thing is that you fit in the time - even if it varies. Any exercise is better than no exercise. If you can schedule two weight training sessions per week and at least 3 cardio sessions, you'll be on the right track to reaching your weight loss goals. Let me know if you have any questions and keep up the good work.
Good Luck,
Paul