You can save 20% at the gate by joining the Southwest Airlines Rapid Rewards program (free and no airline purchase ever required). Print out the "card" that appears w/ your member info after you submit online and show it at the gate when puirchasing. I don't think there's any better deal going. Have a great time!
If you are staying at Pop you can take the Bus to the MK TTC and catch the Lynx bus for pretty cheap (I think about $3 PP RT). It only takes 21 minutes from the Magic Kingdom according to the "golynx" website and runs all day.