Talk to anyone planning a trip to a foreign country, you will certainly hear them speak about the hassles surrounding "the money". Travelers checks are not as popular today as they were 20 years ago. I remember my first international trip in the mid 90's, everyone told me to take all of my cash as travelers checks. Originally viewed as a safer way to carry cash, with today's access to banking around the world via the ATM networks that operate world-wide, you don't need to take a lot of cash with you.
My advice is that folks sure carry enough of their home currency to handle emergencies. For the two of us, I plan on $100 per week and that is in US dollars. Once you have traveled to your final destination, seek out an ATM to obtain local currency. You will want to access your bank account via your debit card and not a credit card. In using a credit card for a cash advance, you will immediately incur interest charges on the money received as a loan against your credit balance.
Of course, this means that before you leave home, you will need to estimate your monetary needs on vacation and be sure that you have enough cash in your bank account(s) to make the withdrawals you anticipate. For us, we carry two ATM debit cards for two separate accounts, just in case a card becomes damaged and is rendered inoperable when you need to get cash.
Regarding banks and credit cards, we exclusively use Capital One. They have an outstanding internet banking platform. They also have some of the best rewards programs with their VISA and MC credit cards. Best of all, Capital One does not charge a service fee for international transactions (including ATM withdrawals) and they provide their customers with the current exchange rate and do not inflate by some standard percentage rate.
Specific to our trip to Ireland, we obtained the Capital One World MC in order to receive special consideration on our rental car and the waiving of the CDW insurance coverage. Read more about that in the "Rental Car" entry in this journal.
It is my opinion that the worst options for obtaining foreign cash are (1) your home back in the USA before leaving for your trip, and (2) the foreign exchange (aka ForEx) at the airport or in major cities. Banks providing these services generally give unfavorable exchange rates. I believe it is better to access cash as you need it, throughout your trip in smaller amounts via ATM/debit cards.
About using your credit card abroad, you should always request that credit card transactions be charged in the local currency and not yours. Merchants (or banks) will take advantage of unfavorable exchange rates when charging your card in USD rather than their currency.
I have had issues with this a couple of times in the last year, including a moderate sized expense at a safari lodge in Tanzania last summer. During our recent trip to Ireland, I had two experiences where the merchant charged in USD. The amount of money on a transaction or two isn't much, but if you consider what it would add up to over the course of your entire trip, you'll see why it's in your best interest to clarify that you want to be charged in local currency.