It is usually more beneficial to bring dollars with you and exchange this in Puerto Vallarta. You can pay for things in US dollars or pesos, but you get more for your money if you pay in pesos as shops and restaurants tend to give a poor rate of exchange. If you exchange money in a bank, you need your identification with you (a passport is best) and only between $450-$500 USD is allowed per person per day. The best bank rate I have found in general is with Scotia Bank on Calle Juarez near the large Plaza and Virgin of Guadalupe Church.
There are also exchange houses available in Puerto Vallarta. Look around before changing money. The exchange house to the right-hand side of Plaza Hidalgo if you are looking up towards the church at the back of the plaza tends to have the best rate.
It is not really advised to exchange money at the airport (low exchange rate given) unless you are really pushed for time, and are coming straight to Yelapa.
Exchange enough of your money into pesos in Puerto Vallarta to cover all your incidental expenses in Yelapa. Acquire some small bills for tips, etc. There are no ATMs or credit cards here in Yelapa!