Why did they laugh at you and think you were joking? Did you not come across very well?
I'd suggest you write to all your potential employers, including all the shops, cafes and supermarkets in your area.
Make sure your spelling and grammar are correct - ask someone to help you if needs be.
Quite often if you just call in a cafe or shop they will be too busy to see you or take much notice, which may be a reason why you haven't got a job yet.
Also, these businesses may not have vacancies right now, but a letter can be kept on file and if they have a vacancy next week they can then contact you.
Don't be discouraged. Good luck.