All notes are U.S. currency, while U.S. and Ecuadorian coins can be used interchangeably (the Ecuadorian coins are in the same denominations and sizes as their U.S. counterparts).  Do not be surprised to receive U.S. Sacajawea $1 coins as change; they are very common, and yes, as they are legal tender, they are useable back in the U.S.  Euros can be changed at a few places, pounds less so; it's adviseable to have a little bit of U.S. cash on you on arrival.  There are ATMs in the Departures Public Hall (Level 2) and the Arrivals Public Hall (Level 2) at the Passenger Terminal. 

Note that traveler's cheques are nearly impossible to use anymore.  There are few if any banks, including American Express, that will cash them.  You might luck out and get cash for them at your hotel, but don't count on it.  Ignore the old slogan and "Leave home without them."

You are better off relying on ATMs, which are readily available in most towns.  They will be part of the Plus or Cirrus systems and use a four-digit PIN. They usually dispense the full amount in $20 bills; some will include some tens and fives. Avoid using ATMs on the streets; try to use one inside a mall or other building.  If you have a companion, ask them to stand aside and watch for anyone watching the transaction.  A guard watching an ATM machine on the sidewalk is helpful if you must use a streetside ATM - and then going inside the bank to check your money can be beneficial, rather than count monies out on the streets.  Daylight hours for transactions is tourist smart.

If possible, bring at least $50 worth of one-dollar bills to use for tips, cabs, and small purchases in markets.  Making change is a hardship for small vendors and cab drivers.  A good rule of thumb for using larger bills is not to use a bill larger than 50% of your tab (e.g., don't pay a $6 tab with a $20 bill).  Even restaurants can have a hard time making change for a large bill, and you may have to wait while an employee runs out to neighboring businesses to scrounge up your change.

If you need to get smaller bills ($5s and $10s) as well as coin change, the Banco Central (Central Bank of the Government of Ecuador) will make change for you free of charge.  Bring your passport to prove identification.  Hours are from 9:00 AM to 3:00 PM Monday through Friday.  The Banco Central may be found in Quito, Guayaquil, and Cuenca.

Visa, MasterCard, and Diner's Club credit cards are accepted by many hotels, travel agencies, and larger restaurants.  Smaller or budget hotels and hostels probably will not accept cards, nor will many restaurants off the tourist circuit.  Note that there may be a surcharge tacked on for using a credit card.  Discover cards are almost unheard of, and American Express is not widely accepted. 

Some travel agencies will not accept cards because the fees cut into theiir profit margins.  if you are purchasing a tour from outside the country, you may be asked to send a wire transfer from your bank to theirs.  This is a common practice and perfectly safe if dealing with a reputable agency.  If you are purchasing a tour in their Ecuador office, you will need to pay cash.

Bank hours vary, but generally are from 9-4.  Some are open on Saturdays for a half day.  Lines can be long so be patient.  In general, like most Ecuadorians, the bank's personnel will be gracious and helpful, so please don't get upset or insistent if the transaction takes a while or you need to speak with different people.