Angel,
Sorry for the delay in responding. I have been traveling for over two weeks and have not had decent internet coverage.
It is very easy to get cash in Belize. ATM cards work in all of the bank ATMs, at least from our experience. We have Schwab debit cards and we prefer using them because Schwab reimburses its clients for any international bank fees charged when you take out cash. The Belize banks do charge a fee for giving you money internationally. I am not sure if other bank debit cards also reimburse you.
Personally, we have set up a bank account in Belize. So we prefer to transfer money from the USA once a year and then take money out from there usually, since we live here full time. But if you are only here part-time and want to use your bank card or credit card, that will work.
It is more difficult for Americans to open a bank account anywhere overseas than in the past, including Belize, due to the FATCA restrictions and regulations. It’s best to open an account in person. You will need two recommendation letters from a banker and/or financial advisor, who are willing to vouch for you. They need to be willing to be contacted by the Belize Bank. Bank personnel will actually contact them. And you will need to provide your US Social Security number. That is now a standard requirement. As long as you are willing and ready to do these two things, and do not have a criminal history, it should not be difficult to open a bank account in Belize.