I researched this a couple years ago and was amazed at how difficult it was.
Marinas with travel lifts often will provide car and trailer parking, but often don't have big ramps because they want everyone to pay for the travel
lift instead. Most
ramp facilities I came across allowed long term trailer parking but not car.
I believe Crandon would store a car and trailer, but it was prohibitievely expensive. (5-week cruise)
I ended up launching at Indiantown instead. There is a seldom used, double wide public
dock which has no tides, and little wave action, with tons of
rigging room. I camped the night before on the boat at the St. Lucie Lock campground and stored my boat at the Indiantown Marina for a fraction of what anything in the
Miami area costs. The two are a mile or so from each other, but it was easy to use my dingy for the shuttle vehicle. (There is also an affordable
storage facility in Indiantown located on the road to the marina, but it was often full when I inquired. (I believe it was called In & Out Storage)
From Indiantown you can get to Stuart the day you launch and it's an easy day from there to Palm Beach. When returning it's fast and easy to just use the Gulfstream to just
head directly to the St. Lucie inlet and back to Indiantown. Since I was coming from the north, this also meant I did not have to deal with the busier traffic found further south while trailering a 26-foot boat.
This of course was for an Abacos trip, not Bimini, but just point it out as another option to consider for anyone
Bahamas bound with a trailerable boat.
The other option I considered using Crandon was to leave my vehicle and Trailer at a self-storage facility on the outskirts of town and take either a taxi or bus back. The other deep
water ramps I found were located at the park at the base of the bridge at West Palm which had storage facilities up the road and one in
Fort Lauderdale, which also had parking issues.