does Harborside take credit cards?

Debit

Both

I was told CASH or DEBIT

Both credit and debit also ATM on premise

No, debit only. They also have ATM machines.

There's an ATM that can take either, and they also take cash

Harborside accepts cash and debit card, but no credit cards at this time.

No

Debit cards. Not sure on credit cards