A 6 months validity passport is enough for most countries.
You might need a yellow fever vaccination before entering the country, but this depends on the country you’re traveling from. The best is to check with your local health organization.
In Panama city you will find various ATM’s where you can withdraw cash with your card. Panama is a dollar economy and uses the US dollar. You cannot get money in the San Blas, so if you want to buy souvenirs make sure you have cash with you!
Don’t bring too much, people often end up using half of what they bring. It’s hot and warm so forget about bringing warm clothes. Bring sun protection and enough $1 bills as the Kuna’s never have change in case you want to buy something.
You must always carry your own travel insurance.