First of all the price sounds like price gouging which is illegal and since Charlie Crist is running for Gov. he is agressively chasing these. Second, I went to Sunbiz.org and searched for the company listed. I couldn't find them. Couldn't find the Mr Falanga as being registered with the state. The only A. Falanga in their list was associated with a diving related business. He also hasn't registed as a fictitious name owner. I'm not a lawyer but it certainly sounds like this "company" isn't legit. There is also no way a lein can allow them to sell your house. That would take a court action and foreclosure. Lastly, according to the search I ran, the Miller Act is a law that requires contractors doing federal work to file a surety bond.
Again, I'm not a lawyer but I'd imagine some con artists saw the blue tarp and decided to send you and about 500 other people this same letter. Florida is well known for the scum bags who prey on homeowners on construction related issues.
I checked sunbiz too. I also did a License check at DBPR Construction Industry Licensing Board. I sure see SCAM. Guess the idjits that sent the letter did not know us Freepers don't have MORON in lights on our foreheads.
Tourist season is also fraud season. The cons also like to travel south. Maybe Gypsies got tired of false roof and driveway repairs as a way to earn money.