I don't think OP is anywhere near an airport that Allegiant flies from
The drive from St. Pete to Orlando is a pretty smooth and easy one once you get on I4. About an hour and a half or so, provided there is no bad traffic.
I've done the drive from Tampa several times, and it's been a snap.
St. Petersburg-Clearwater International Airport to Walt Disney World is about 85 miles. Except for the very beginning and very end, it's all freeway (I-275 and I-4) -- so, in theory, it should take as little as about 90 minutes.
The problem is that the route goes through Tampa. Maybe I'm just always trying to drive through Tampa at the wrong time, but I always seem to get stuck in long, slow traffic jams whenever I drive through Tampa.