I left a career in marketing at age 26 for a shot at medical school. I had a degree in journalism, a 3.2 cumulative gpa but nearly 0 science classes because I had a BA. I started completely over and took all my prereqs in one year. Ended up getting As in every class except a C+ in Organic II. I was very dissatisfied with my Organic II grade so I took Biochemistry the next semester and got an A. Also while I was taking classes, I got a job scribing at a local hospital and took my MCAT (actually, I took it twice because I got a 6 on the verbal reasoning the first time). I am now 28 years old and will be a M1 at KU in the fall. I would STRONGLY encourage you to not give up. If you are committed, you will be able to get in, although it might possibly take a few years.
Dont know if more undergrad classes are an option for you, but if you can, Id retake some (or maybe all) of those prereqs and do well this time. It worked for me anyways.
Also, if you live in a big city, look into a scribing program. As I understand it, many hospitals are transitioning to electronic medical records, and it is a popular trend for docs in the emergency department to hire scribes to fill out patient charts. It is fantastic experience that will stand out on a med school application and it will help to reinforce your decision to pursue a life in medicine. Dallas / Ft. Worth has an extensive scribe program, go to
http://iamscribe.com/ for more info.
If you live in a small city and scribing is not an option, volunteer at the nearest hospital. Even if its only a few hours a week, they probably need help. Volunteering looks great on a resume and you'll probably get the added bonus of feeling great because you are donating your time to helping other people.
As for Caribbean or Mexican medical schools, Id do those as a last resort. As I understand it, those students have a far more difficult time getting into residency programs than US medical students. Osteopathic schools tend to cater to more nontraditional students like yourself, so that is an option as well.
Anyways, dont give up. Youre certainly not too old. You can do this, despite what others might tell you.