I have just been notified that my wages are fixing to be garnished 25%of my check for a medical bill. Under Florida statue 222.11 my wages are exempt from being garnished. We use a leasing company to handle our payroll. How do I go about making sure the payroll company does not deduct any money from me?

Not up on 222.11, for what reason is your wages exempt ?

If you know of the court garnishment, you may have to produce this evidence to the court, A place of business has little ability to ignore a court order once it is served to them,

From my understanding the statue states that the head of household income is exempt from being garnished.

The federal limit on wage garnishing is 25%. Does this leave it up to the business what % to garnish out of the employees' wages?

First who notified you? Second, have you contacted your payroll department to inform them of your exempt status?

You are correct in Florida the Federal exemptions do apply

Federal Restrictions on Wage Garnishments

And if you are head of household you can get up to a 100 pecent exemptions. You would need to inform ( I would do it in writing) that you are expecting a garnishment and you are exempt under that provision.
Now this is the issue, I am not sure they can just ignore the court order, so you may have to file to have it dismissed in court under that rule.