Should you cancel your trip or reconsider going? Nope. I didn’t during the previous crisis even though their were mass protests in Athens. The city was kind enough to not start crap while I was there. I have that effect.
If you are planning to get some sun in Mykonos and Santorini or enjoy the street art (or artful graffiti) of Athens, bring cash. As the Wu-Tang proclaimed, Cash Rules Everything Around Me.
It’s a quick lesson in Greek life, the population has a habit of not paying off credit card debit. This puts banks in trouble. Local businesses suffer for it. End result, credit cards won’t be accepted.
Right now, banks are running out of money, so you should plan accordingly. Contact the hotel of your choice and ask if you need to pay in full before hand. Plan out where you want to go and the cost. You just don’t want any surprises and you don’t want to carry around a wad of unnecessary cash.
If you are planning to visit, Athens and the major islands can be done in 2 or 3 nights each. You can get great meals for under 10 euro. Sit down restaurants are for the old folks from the cruise ships.