I don't think anyone is going to know. The last 5 trips I've taken to WDW we've had a car and no one ever asked for plate information or gave us any type of parking permit (I do remember years ago they would give you a print out for your dash). I was at the Poly in the fall and mentioned we had a car, they didn't care, no vehicle information taken, they only thing they told us was where to park. The security guard never recorded the plate, either. Just scanned our MB and let us in. I watched to see if they were writing down the plate number after, they did not - it was too busy! I know there are cameras but I really don't think they are enforcing anything. If you are staying at a resort without direct park access (All Stars/POR/OKW/SSR/CS/even CBR) I don't think they care. There really isn't any way for them to know you aren't staying aside from running plates for every car and cross referencing them with a resort guest list - and they are NOT doing that. And if it's a rental car, running a plate won't get them much! I wouldn't worry about it and park your car in a less busy location. Security is used to seeing cars parked in the same spot for a week or more at a time. If they even actually notice. But, parking at the Port may be around the same cost as taking Disney transportation to and from the Port, for convenience sake (especially if you aren't staying at Disney after your cruise), I'd drive myself and park in the garage there. It's an easy drive.