We like the flexibility of having a car, so even when we lived in CA and flew to FL we rented a car.
We have stayed onsite and off. When we stayed on site we rented vacation points from a DVC member and paid $99 per night with no additional taxes. That was for a Sun.-Thur. night stay at Old Key West. It was great, but still very expensive.
We have found for us that staying off-site, even if we rent a car, is far cheaper. We stayed at the Marriott Courtyard for $38 per night, Doubletree Villas for $42 per night and then our last trip was at Vacation Village (condo) for $260 for 7 nights. ($36 per night)
The condo was the best deal for us by far. It came out to $36 per night including tax and had a kitchen-ette, 2 TVs, a washer and dryer in the unit. We ate b-fast in the room and had a fridge for milk and such. We also sometimes ate dinner in the room. Just pizzas and such, but it was more relaxing than having to go find a place and eat out with 2 very tired kids who really just needed to get back to the room and relax.
Last time we went to Disney and had to rent a car we got an economy car for $12 per day. If we stay in a condo for $36 per night and rent a car for $12 per day, that is still a big savings off of staying on property and it gives us the flexibility to go anywhere we want to eat, play, etc....
This is what works best for us.
Dawn