Ahhhhhh Help!

$20 backless booster from toyrus & the cabs seatbelts

I suggest that if the law requires the use of car seats in a cab that the cab will have one. I also suggest that for the short distance between the airport and your resort it would be ok to not use a car seat unless they're required by law. There is such a thing as over thinking/overdoing the safety issue.

If you want to know ahead of time, call a cab company there.

After reading the post about the pillow, please do not do that. If the seat belt doesn't fit over his shoulder correctly the pillow will not protect him. Just a sudden stop could injure his neck/head. A pillow will also not work as a booster. It is not firm enough to hold him to the seat. Do not use the seat belt. have him sit on the seat without a seat belt or seat him on the floor. He's less apt to be thrown if there is an accident. It's highly unlikely that there would be, however.

I've heard that carseats are not required in cars for hire (cabs, limos, etc). You can call a cab company in FL and ask about that to verify.
Another option is to check the car seats through...airlines typically do not count them as luggage or charge for them.

Will the resort you are staying at, provide a pick up and drop off service?

Airlines do check the car seats in at no charge. You gotta decide if you want to take the bulky item, in my case, I did not, too much trouble! You don't need one for a cab. Possibly purchase one once you get there if you find you really need it...purchase from a resale shop or the local Wal-Mart. It seems it might be less trouble than taking your own.
Have a fun vacation!

Maybe call some cab companies around your destination point, and find out if any of them have car seats for people in your situation?

If anything, you could always check your carseat, so you don't have to haul it around the airport... When I flew with my DD, they allowed us to check it for free... (I cheated a bit when I flew... I stuffed the car seat bag full of the things that wouldn't fit in my carry-on, in addition to the car seat itself so I wouldn't have to pay for extra checked baggage...)

Most airlines don't charge for you to check his car seat, it doesn't count as baggage. You can check it with luggage instead of gate checking it. At four, you can use a backless booster too. If you are comfortable going that route, for the distances you are traveling, it will save you some bulk. I have heard many horror stories from friends who rented car seats and arrived to find the wrong seat was reserved. Better to be safe than sorry.

I believe Anita is correct about the car seat laws. Is he big enough for a booster? I might consider purchasing a booster seat here and then taking just the base part (if you get one with a back that is) on your vacation. That way it'll be lightweight and easy to pack. The airline will check it for free regardless but I believe boosters are not allowed on the airline as they are not FAA approved for impact.

A lot of the resorts in FL offer car service as part of a room package. Check with the resort you're staying at to see if they do. If so they should provide a car seat as long as they know they need to.

I don't think car rental companies rent car seats (liability issues) we've always had to bring our own and check it at the gate.
I'd make a few calls ahead of time re the laws and requirements, you don't want any surprises when you get there!

He is almost 4, he can wear the cab's seat belt. Bring a travel pillow to place in between the car seat and his shoulder/neck if he is too short and sit in the back of the cab/car with him.

You can also use the travel pillow as a cushion for him to sit on as an alternative booster seat and use the car's seatbelt.

Its best to have him secured than to have him sit loosely in the car if a sudden stop occurs and throws him forward. Just my 2cents - safety vs luggage..you decide what works best.