If you take the Turnpike (I think it's about $11 to get to disney, maybe just a little more). It will probably take 3 1/2 hours with decent traffic. You can save money by going I-95 then hitting the turnpike at Ft Pierce, but getting through traffic past Ft Lauderdale and Palm Beach can be a nightmare, esp. if it's rush hour.
It always seems to take us longer going I-95, so for us it's worth the extra toll money to go the turnpike the whole way.