Of course you will need to exchange money while you are here, especially for those who come to Vallarta for just a vacation. Here's the 411:
Banks will not exchange your money.
Airports are the WORST place to exchange money, with hotels being next in line.
There are lots of money exchange booths littered around downtown. These will give a better rate than the hotels and airport, but still not the best.
What is the best exchange rate you ask? COSCTO! Who would've thought, right? Now they won't actually exchange all your money, but you can pay with dollars and get your change in pesos. This means you can buy a $1 churro with a $100 US dollar bill and get the change in pesos at the best exchange rate in town!
For those living here for an extended period of time, it's best to set up a bank account so you don't have to do to costco so often :)