About seven years ago, I moved from Miami to Orlando. During my trips between Miami and Orlando, I used to take the Turnpike all the way. Then I discovered it is just as fast and much less expensive to use the "BEACHLINE"(528) and I-95. The Beachline (a.k.a. 528, formally known as the Bee Line) is an East-West running highway which connects Orlando with the East coast of Florida which includes: Cape (Port) Canaveral, Melbourne,Titusville,Cocoa Beach and others. The Beachline (528) runs alongside Orlando Intl. Airport (MCO) and is very accesible when driving from there. Just make sure to look for the sign 528/Beachline EAST. Once you get on the 528 Eastbound, you will then have a straight shot East for about 40 miles until you reach I-95. From the airport to I-95 (on 528) there will be one toll costing $1.50. This will be the only toll you will encounter along your trip to Miami. On the Turnpike, it's a whole different story (about $14 in tolls, ONE WAY!). Eventually, after 40 miles on the 528, you will reach I-95. Make sure you don't miss the off-ramp to get on I-95 South. Otherwise you will end up in Port Canaveral (many other cruiseships dock there, including both of the Disney cruiseships). From there is about another 200 miles heading South on i-95 until you reach Miami. I believe you leave I-95 in Miami using 395, which should drop you off on Biscayne Blvd in downtown Miami. The entrance to the Port of Miami is on Biscayne Blvd right next to the Bayside Mall. And from what I heard, the American Airlines Arena (where the Heat play) is right across the street from the port entrance (I left Miami before they started building the A.A.A.). From there, after entering the Port of Miami, I am sure there must be signs pointing the way to cruiseline(ship) and the respective long-term/passenger parking.
When returning to Orlando, be careful when getting back on to 528 from I-95 Northbound. It can be tricky (if my memory serves me correctly). You will need to be in the right lane long before the 528 overpass, and before your access to the exit lane is blocked by concrete barriers.
So I hope all of this can be of some help to you. Goodluck and have a great time on your cruise.