The historical record in the Atlantic basin (includes the entire Atlantic Ocean, Caribbean Sea, and Gulf of Mexico) lists 280 tropical storms, of which 158 became hurricanes and 53 became major hurricanes (Category 3, 4 or 5 on the Saffir-Simpson Hurricane Scale) according to The Deadliest, Costliest, and Most Intense United States Tropical Cyclones from 1851 to 2006 (see http://www.nhc.noaa.gov/Deadliest_Costliest.shtml).
Of course, it is reasonable to assume that some tropical cyclones went undetected before the geostationary satellite era which started around the mid 1960s. The numbers of tropical storms, hurricanes, and major hurricanes over the entire Atlantic basin from 1966 to 2006 are 74, 40 and 13, respectively. It is interesting to note that in both the geostationary satellite era and the period before 1966 we average 1.8 tropical storms, 1.0 hurricanes, and 0.32 to 0.35 major hurricanes in the month of October. Most of the other months show an increase in the averages during the geostationary satellite era.
So what does this mean for the United States and South Florida in particular? The records should be better for U.S. landfalling hurricanes given the fact that these events have a greater probability of being detected. There have been 51 hurricane strikes in October in the U.S. mainland since 1851. This means that we average 0.33 hurricanes hitting the U.S. per year, or one about every three years. It should be noted, however, that it is still likely that some hurricanes hit less populated areas and were not detected, especially before 1900.
If we focus on major hurricanes making direct hits in Florida during the month of October, there are only 10 on record going all the way back to 1851. Although this is an extremely low number, it should be noted that most of the U.S. major hurricanes in October occur in South Florida.