Yes you will need a passport with at least 6 months of validity left. If you do not have a passport currently you should apply for one ASAP. Passports can take months to recieve.
No visa is required, but proof of a return ticket is required.
The resort is all-inclusive! All food and drinks (including alcohol) is included in your stay!
Costa Rica is not in the hurricane belt!
Costa Rica has a tropical rainforest climate! The weather in September will be warm and humid. The mornings are usually sunny and dry with occasional rain showers in the afternoon