I think this is a very controversial topic and many experts differ when is time to make the main decision: Cash or Credit Card when traveling outside your country most specifically a country with a different currency; so here's my input in case it can help you clear the dilemma.
Before we start, let's be clear that this is advice is for your doubts on daily usage money only, meaning that your travelware, hotels, flights, special events, car rental, trains and all that predetermined stuff will be bought online with a Credit Card.
Think about these pointers first:
1. Determine how much you are willing to spend in your stay
Yeah I know, same ol' budget BS… Trust me I HATE budgets; matter of fact, I SUCK at even trying to make one, but here's my hack: I put a daily limit of how much I am willing to spend per day. This will include food, drinks and whatever you do! Just put a daily limit of how much you will spend. Then you multiply that by the days of your trip. IE, ($ 50.00 Daily Limit) x (7 Days) = $ 350.00 for spending money. You can always go over that but it will keep your focus on an specific amount that you will try not to exceed (even subconsciously).
2. Determine if your currency is weaker than the country you are visiting
So , if the exchange rate is one Dollar = 50 pesos (in my case), or one Euro = $1.16 Dollars, you might want to consider using cash instead of your credit card and here's why: Credit card exchange rates may vary and you might lose a bit more (not necessarily but most of the times). So check with your bank first.
After you are clear on the above two steps you might consider these pointers:
• Cash will help you have a real-time status of what you are spending
If you determine that you will spend $50 per day, go out with $70 and leave the rest somewhere safe or apart from you usable money. Don't panic! In case you go over it you will have your CC (for emergency only)
• Credit card can be used for special occasions
Like an expensive dinner or a day of shopping.
Long story short you will need both and here's the breakdown:
1. Cash for daily usage (meals, snacks, public transportation, unexpected)
2. Credit card for flights, trains, concerts, hotels and emergencies. (All the default stuff you buy online prior + expensive emergencies)
But ultimately, be mindful of your spending abroad and keep it simple. Cash will help you stay in control when you are out of your routine and credit card will make you check and balance when you go back home and pay, that's why I recommend putting flights and hotels here and you'll get no surprises when checking your statements!