Hey Candy (aka Liz) nice new profile pic!
An airport taxi does cost a bit more than that…I think to get to downtown hotels (Fiesta Americana, Sheraton) it's about $18 (US$) or so.
Old Town/Zona Romantica and also the southern part of Nuevo Vallarta (Vallarta Palace, Paradise Village) is probably about $24 (US$) or so.
And besides ignoring the "timeshare people" also ignore "hotel" and "taxi" timeshare people. If you are going to take a taxi from the airport only buy your ticket at a taxi booth. I think there are 2 ticket booths there…one booth lists fares higher than the other…so check them both. Airport taxi fares are set prices and are priced by zone. You can pay in either US dollars or Mexican currency. It is usually better to pay in pesos…there are ATMs there.
If you don't have much luggage…you can also take a "non-airport taxi" which costs less. When you pass all the timeshare and taxi people and go out of the building…to your left you'll see a ramp which leads to a bridge that crosses the main street to off property taxis (and buses too). Again, always ask the taxi driver how much before even getting in…some drivers will barter.