Mexico charges an airport departure tax of US$18 or the peso equivalent for international and domestic flights. This tax is usually included in the price of your ticket, but check to be certain. Traveler's checks and credit cards aren't accepted at the airport as payment for this, but U.S. dollars are. Jalisco and Nayarit charge a 2% tax on accommodations, the funds from which are being used for tourism promotion.
Puerto Vallarta and environs have a value-added tax of 15%, called IVA (impuesto al valor agregado). It's occasionally (and illegally) waived for cash purchases. Other taxes and charges apply for phone calls made from your hotel room.