Other than the area directly around WDW on 192, and to a lesser degree the area right around Universal, and the zoo known as I-Drive, traffic isn't affected by the theme parks. Trust me, there's LOT more to this area than theme parks.
Mornign rush starts around 6:00 am, gets very heavy from 7:00 to 9:00 am. Evening rush starts around 4:00pm and stays pretty heavy through around 6:30 pm.
Anne