School Calendar is here.
http://www.fldoe.org/districtcalendar/
Arriving early when staying on site is subjective, I always suggest getting an early start. Some like to sleep in, others go commando.
Yes, you have FOTL, BUT, the crowd arrives between 11am and 4pm and the walkways are crowded. Not to mention, the express lines for the major attractions at those times can be 20 minutes. For example, the line for Hulk at noon will most likely be 20 minutes.
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Reasons why you want an early start, even if you are staying onsite and have FOTL.
Show up at the gate at 08:00am, go in first, and get a front seat ride on Hulk and a back seat ride. The perfect way to start your day.
Dr. Doom, walk on
Spiderman, walk on
Head to the back of the park and ride both sides of Deuling Dragons in the FRONT ROW of each coaster. FOTL can get you on the ride quick, but not in the front row.
Continue around the park doing the water rides.
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Other option after Spiderman is to head directly to Pteranondon Flyers and get 3 rides before the kid rule goes into effect. This is a pleasant ride, but a lot of fun when you can walk up and get your ride. FOTL does not get you on this ride, you must show up early before the kid rule goes into effect.
So basically, I'm saying to show up early so you can get front seat rides on Hulk, Deuling Dragons, and ride PF before the kid rule.
Trust me, showing up early counts. It's the key to a great day.