Will it be a problem is we bring some $50 US bills to change at either a bank or to pay a tour operator with? I read they are treated with suspicion, and don't want to bring them if we won't be able to use them.

Thanks for your advice.

Not sure what country you are talking about. It is not a problem in Mexico- but all bills must not be torn, damaged in any way or have writing on them. Banks, Casas de Cambio, etc. are very strict about this.

DO YOU WANT PEACE OF MIND, USE YOUR CREDIT CARDS.....NO NEED TO BE WALKING AROUND WITH CASH.
CREDIT CARDS ARE ACCEPTED ALL OVER LATIN AMERICA, IF THAT IS YOUR DESTINATION.

Sorry, the country is Costa Rica

Hi there, I would not bring $50. bills. My husband tried to pay with one at a gas staion. They disappeared and then came back with a torn one and said they could not take it. My husband did not give them a torn one but we did not care because it is a not a problem in the Us. They are very leasry for some reason of 50' and 100's

I too wouldn't suggest $50 bills... If you have an ATM card (Plus sytem) then use ATM's in Costa Rica to get cash from your account at home when you need it. $50 and $100 bills are very hard to change and many places (restaurants, stores and small hotels) just won't accept them.
Most tour operators would accept traveler's checks and if you are going to change the $50's in a bank you may as well change a traveler's check - much safer.
Cheers,
Andrew

Take 20's in good condition then you won't have to worry about it.