Is doing a hour of cardio and a 20 minute ab work out every day good enough to get a six-pack?

Yes - it should be effective. Cardio 5-7 days a week, depending on how so you want to lean up - diet is the HUGE key when trying to shed poundage - cut out the soda, nothing with high fructose corn syrup, diet sodas aren't even what they say they are alot of the time - no junk food. To rev up your metabolism, try 4-6 small meals a day, and make sure you jump start it in the morning with a proper meal.