Things to get ASAP
You will need a valid passport that doesn't expire for least 3 months after the date you'll be in the country. You can apply for it at the website below. You may need to rush it if you don't have one yet.
https://uspassportandvisa.org/us-passport/
If you plan on renting a car, you will need an international drivers license. You can get one at your local AAA and it's about $20.