Even though we live in northeastern Florida, the so-called "Florida winter" in our area can get fairly cold. Been living here since January 2009 and have seen daytime high temps of 45 degrees, with overnight lows in the mid-to-upper 20's. When we thought about moving here, we had no idea it could get that cold here. Some mornings even have to use our ice scrapper, bought when we lived in Colorado, to scrap off frost from vehicle windshield.
Before getting a new block put in, we'd start the boat up a couple times a month during the Florida "cold season" and it was fine. Now that we have that new block, we either do the minimal, which is drain each side of the block or have the boat winterized.
Many people here say "winterizing a boat in Florida is a waste of time and money". We, along with our marine mechanic, don't think so. Being safe is better than being sorry and ruining the engine.