personally, I would drive my self, pay the $12 parking, it is $3.00 after 6pm. you take I-4 get off at exit 74, take a left at light, be in far right lane, and follow sights to theme park (stay right).
That way you and come and go a your leisure ( you have re-entry with paid parking), and not be at the mercy of the buses schedule.
Check out the annual power pass for $149.99, and utilize the "flex-pay" feature , and you can have unlimited 2-park entry for a year (from the date of first scan) for just $12.50 per ticket plus tax. It does have 3 black out periods though - Easter week, 4th of July week, and at Christmas.
Makes the financing of a vacation a little easier, and frees up money for other things.
ENJOY YOUR TRIP!