The local currency is the colón plural, colones named after Columbus Spanish: Colón CRC.
As of December 2014, the exchange rate was 536 colones per US dollar. Money exchange is provided at most banks; however, it is recommended to do so at the state banks, especially the Banco Nacional, since they have lower rates. There is also a money exchange service at the airport, but it is outrageously expensive. But note that the use of US dollars is quite common; in the tourist setting, almost everything is priced in dollars but sometimes prices are cheaper in colones. Note that when a price is quoted in "dollars", the speaker may be thinking of a dollar as 500 colones; so it is always worth checking whether this is what is meant.
You can find ATMs in most places. They normally dispense US dollars and colones. With Visa you get money at almost all ATMs. If you've got a MasterCard try the ATMs in the AM/PM supermarkets, they give you up to 250,000 colones c. USD500. Another option are the ATH-ATM's but they just give you up to 100,000 colones c. USD200 each transaction.EC-Cards European are accepted on all ATMs. The limit is usually only set by the Card. In addition, drawing money with your EC-Card will almost always give you a better exchange rate than changing cash in a bank.
It is also very common to pay even small amounts by Credit Card Visa, Master Card, Amex is less common.
Keep in mind that most banks and credit unions charge not only fees to get money out of an ATM in a foreign country, but also a foreign exchange fee usually 2% or 3% for the amount of the transaction. So to withdraw USD100 worth of colones with your ATM debit card you could pay a fixed fee to the ATM operator often USD3 or more, a fixed fee to your bank USD2 or more, and then 2% to 3% of USD100, so you end up paying USD108 for USD100 worth of colones. Paying a merchant directly with your card only incurs the foreign exchange fee.
You might get a discount such as between 5% and 10% when paying in cash, but it is not common enough to be expected. Also, it is not really necessary to get colones at the airport because you can pay everywhere in USD and receive colones as change. Most places except smallest restaurants take credit cards and many places including the gas stations take American Express.
Traveler's checks are rarely used. When paying with traveler's checks, unless for hotel nights, change them first at a bank. Expect long delays with traveler's checks at the bank, lots of stamping, the higher up the official at the bank the more stamps they have. Dollars are easier.
The most common souvenirs are made from wood. Unless it's marked as responsible plantation grown wood, it is most likely not and may be contributing to the deforestation of Costa Rica — or even Nicaragua or Panama!
Most visitors returning home are not allowed to bring back any raw foods or plants. Accordingly, the single most desirable commodity for visitors to take home may be roasted not green coffee,considered by many as some of the world's best. Numerous web sites explain the fine qualities of various growing regions, types of beans, types of roasting and sources for purchase. Best prices come by purchasing several sealed bags of 12 ounces or so, but you can also buy in larger quantity if you look hard enough the Mercado Central in San José has a coffee vendor that sells many varieties, including organic, by the kilo. And experts definitely recommend buying whole beans entero: in any kind of storage, they last longer, and ground coffee sold in Costa Rica often contains sugar because it preferred by locals -- if you want pure coffee without additives look for "puro" on the package. The stores in San José airport will sell you excellent coffee, but other good quality blends can be found in local supermarkets and direct from the roasters. It can be an expensive but delicious habit. If you're serious about your coffee, bring at least a partially-empty suit case and fill it with perhaps a year's supply web sites explain how to store it that long. Take care with tourist outlets especially at the airport where small quantities may cost as much as ordering on the Internet.