There are only four venomous species of snakes in your area of Florida... the Eastern diamondback rattlesnake, cottonmouth, pygmy rattlesnake, and coral snake. Learn what those four look like, and you'll never have to worry about it again.
Racers will eat anything they can catch that they can get down their throat, lizards, frogs, toads, other snakes, rodents, small birds, etc. Whoever told you hognoses eat other snakes, don't believe them... hognose snakes feed nearly exclusively on toads... indigos feed on other snakes, but are generally larger, bulkier, and more iridescent than racers.
This is also the time of year to find snakes trying to come into your house, and this is why... it's freakin' HOT outside!! they feel your air conditioning coming out through that little gap under your door or what have you, and they know it's more comfortable inside than outside. What that one sounds like to me would likely be a crown snake.
Sounds like you've got a nice yard. Enjoy it.