Currency exchange

This subject divides into those who like to have some currency for odd things, and those who haven't used cash for donkey's years.
I like to have some cash available for odd purchases, toilets and when the electronic systems have failed, as has happened several times this year throughout Europe.
I like to have 300 euros tucked away.
Your call, depending on how you feel.

There just isn't a right answer. Some are cautious so they like to have cash when they arrive a country. Some wait because they are frugal and its typically cheaper to get cash when you arrive the destination. On a 4 week trip to New Zealand, we didn't need/get cash until the 3rd week. On one trip we were in Switzerland for just 2 days and never did get cash. In Portugal, we used very little cash. No more than about 100 euros for an almost 4 week trip.

I can't recall having to pay for public toilets in Portugal, I do recall needing cash sometimes for parking.

In the last couple years on our travels, I feel like we've had more cases where only credit cards were accepted in contrast to situations where cash was required.

I closed my Wells Fargo account and opened up a Charles Schwab for no fees. I also use my credit union's debit card. Portugal has a lot of Euronet ATMs. Avoid those and use bank affiliated ATMs, preferably during banking hours.

One thing we do that makes things easier is that at the end of a trip, we will bring home about 100 euros to start the next trip. Our next trip is to England and we won't withdraw any pounds until we get there.

You've received great advice! I would ask if you have used your credit union debit card outside the US previously and with success? If so, great news!
I ask because my bank is small and local and I no longer take/use their cards (debit or Visa) because inevitably it triggers a fraud alert- even if I have called or set a travel notice prior to departure.
Having a back up card is another sensible precaution. If you are looking for a Wells Fargo alternative, I'm really pleased with Capital One (no fees) and have never had any issues with it. I like the 360 online checking tied to their MC. I transfer some $ from my bank into the 360 account before departure (it takes a few days to clear) and then pay off any debit card purchases they occur.
I like not accessing my little US bank for anything, even with a VPN, when traveling.
I'm also of the have some local currency camp upon arrival!
Safe and fun travels!

Get euros before you go? No need to, but if you will feel more comfortable having some cash in hand, go for it, it will cost you 5-7% above the posted exchange rate, but many feel that is worth peace of mind. How much? at most a 100 maybe 200 euros, but that is a lot.

Use an ATM once there? That is what most do. Expect you may have to pay a 3-5 euro fee to use the ATM. Read up on Dynamic Currency Conversion (DCC), that has the danger to cost you much more, Besides what your bank may charge in fees, an ATM is the cheapest way to get cash. Again, I would not get much, maybe a 100 or a bit more to start.

Once there, use a credit card for everything, tap to pay, either with the card or Apple/Google pay is now the standard way to pay for things, even small purchases.

In Portugal, I did run into a restaurant or two that was cash only, and they were some of the best, local, small places I have eaten. I assume the tuk tuk drivers take cards, bolt is all card, no need to tip above what is on the app, no tipping in the real restaurants (tourist places may angle for a tip when they hear your accent), even most places in the markets take cards.

My general experience has been I use card for 95% plus of my purchases, but every trip, I run into needing, or wanting, to use cash, But then I probably venture off the tourist path a bit more than average.

We took a guided tour last Fall in Lisbon and our guide warned us that cash is king in some pockets near Jorge Castle. Sure enough, the first restaurant we went to was cash only. There was also a small grocery store near our hotel that had a surcharge on credit card payments under €10. Other than that, we used credit card. We typically find an ATM once we arrive and take out some cash for circumstances like this.

I like to bring approx 100 euros with me so I don't need to worry about finding a bank. Now, there are lots of ATM machines, Euronet, which charge a higher fee, but I have found it can be a bit challenging to actually find a machine tied to a bank in Lisbon, and when I do, have had bad luck that the machines were out of cash. I like that bit of cash, just in case. Who likes to eat at a cafe and find out their machine is out of order and have the awkward moment where you only have a card. Been there a few times, and having euros took care of that. Anyways, the fee for a few euros is not much and then you just don't need to worry about that while enjoying vacation. And then, when you run into a bank while wandering around, you can pull out a few more euros to bring home for your next trip, that is if you used those 100 euros.

I had Euros from a previous so didn’t need to exchange any while there. I will simply say that some businesses only accepted cash, including one petrol station that I didn’t realize was cash only until I had started pumping fuel.

When using a credit card at a food market, try to ensure they charge in Euros. There was one in Tomar that charged in USD since my card was from the U.S. the cashier didn’t even ask which I preferred.

Google maps is great. If you type in ATM nearby, it will show ATMs and even what kind.

When using an ATM, go for the ones that are actually in a bank or that belong to a bank. Do not use the random ones you find on street corners or in stores, etc.