Many large chains, hotels, and major restaurants will have the means to accept credit card payments, but your average independent store will not. In touristy areas, it is more common for businesses to accept card payments, but more often than not they will be cash only.
It’s not wise to carry a ton of cash with you in Guatemala because petty crime is relatively common, so try to plan out your daily expenses and carry only the amount of money you expect to need.
If your bank charges hefty ATM fees, withdraw a big lump of cash every week, and store it in various compartments throughout your luggage which you leave in your hotel. This way you can skip the ATM fees, and not have to be worried about carrying excessive cash on your person.