Florida – ending lease question

So thanks to the help of Myfico I am in the process of buying my first home.  I am supposed to close on my home the end of this month,  I am currently renting and my 2 year lease ended 2/28/10, my landlord said I can give him 30 days notice when I am ready to move.  Here is my question Can I give 30 days notice from tomorrow 3/12 to 4/11 or do I have to wait and give it on 3/16 to 4/15?  The reason I ask is because florida law says:

“When the tenancy is from month to month, by giving not less than 15 days’ notice prior to the end of any monthly period; “

So does this mean in order to get back my security deposit I can’t end my lease until 4/15?  I am so confused and I don’t want to lose my security deposit as I don’t trust this Landlord.