US $ in Equador

they don´t just make sure they are real!
bring plenty of change, having fives and ones is easier than tens and twentys

From my experience you won't be able to get rid of torn notes (ie pieces missing out of the note). Old/worn/marked notes are probably OK.

Be aware that $100 dollar bills are really hard to use here and really will only be accepted at banks and when making large purchases (like paying your rent/hotel or for your language school etc.) Also be wary of counterfeit US bills received in other countries other than the US. I was passed a counterfeit bill in Argentina and it was discovered to be false by a bank here in Quito. Even a $20 bill can be difficult to use here sometimes depending on what you are trying to purchase. Also once you get here make sure that you get in the habit of paying for things with your coins that you have received as change otherwise you will be drowning in "monedas" because, remember the silver dollar that you used to receive as good luck from the tooth fairy and was a rare find in the US. They are rare in the US now because they are all down here and people love to give them back to you as change as well as giant plate sized 50 cent peices so that you can go jingling down Amazonas alerting every would be criminal in the immediate vicinity that you are loaded down with cash.

I have to warn you that some traders (ie shops, reataurants etc) will try and telll you that the notes you just received from the bank and have the correct marks etc that hey are forgeries and try to get extra so-called real notes from you. Always make sure you get your original (so-called 'false') notes back from them. Not many try this scam though.

That said the $1 and $5 notes are better than $10, $20 etc as thgese are harder to change. Make sure your change isn't forged notes though.

Even though locals will use old bills, expect a double standard for gringos.

I had no problems with old notes. As much as one of the posters said avoid coins, you need them. Only once did an ATM give me low denomination notes and it can be a pain in the butt waiting for a shopkeeper to find another that will change a tenner or 20.

I have had no problem with even the most decrepit note, but that is just my experience.....bring lots of change and 1, 5 notes, if possible, it will make you life easier....