If you want something fast food - Taco Bell (right next door to Discovery Cove) has very good breakfast choices.
If you want table service and a known quantity - Denny's and IHOP are near by, both on I Drive.
For something quicker but not fast food - Panera is also on I Drive close to Aquatica
For maybe a healthier breakfast - Natures Table is on Westwood, it is located in a business park at the very back so unless you know where to look it is not something you just stumble across.
Sadly missing - there are not a lot of local places that serve breakfast near SeaWorld (at least that I know of) so a chain place may be your best pick.