I would not recommend a Taxi. The reason being that taxi's use a meter. If you get stuck in traffic, or if the driver decides to take the long way, you get stuck with a potentially larger bill. Average one-way fare would be $40-$50 (plus tip).
Towncars offer fixed rate services in much nicer vehicles. Typical round trip rates run $90 give or take (plus tip), which is pretty close to what you might pay for a round trip Taxi.
A third option might be the Mears Shuttle. $27 R/T per person. (Plus tip) You don't need any reservations for the Mears Shuttle when you get to the airport. (You will need them for the return trip back to the airport) This option is cheaper, however, it should be noted that the Mears Shuttle *MAY* stop at other resorts before reaching Pop Century, since they will have other folks on board the van or bus.