First solo travel trip

I’m turning 18 in June and I graduated early and have been saving up. Id like to go on a trip outside of the U.S. Theres lots of flights under $400 to places like Cuba, Jamaica, Columbia, Peru, Ecuador, Mexico, Puerto Rico.

I was wondering if it would be safe/realistic for me to go to any of these places alone for my first trip out of the country. Id plan to stay a week or 2 maybe and save up around 3-4k possibly. I’ve never traveled alone outside the U.S before so any advice would be appreciated.