Boaters get the Florida Boating area that is top on my list of the best places to go. What a fun zone to take advantage of the water clarity, boater friendly bars, and fishing that will fill up your cooler with tasty keepers. The ramp is fee based, and it was $30 dollars total. They charge for each launch or pull out the same $15 dollars, so in normal situation it will be thirty. Besides the fee, everything else is fantastic.
$30 dollars to use the boat ramp seems awfully high. You can launch and park the trailer at the Caribbean Key Largo for only $15 total. Down below past mile marker 80 is a nice free boat ramp, just a little on the primitive side.
When you leave the Founders Park Marina, the quickest way to cut over to the Ocean is using Snake Creek. Just go down the islands about a mile to find the entrance on your left to the Snake Creek Channel Bridge.