I am not a gambler but you can use your cruise card as well as cash. We have some big time gamblers on staff, some of them even win, such as "Diamond" Jim C. I'm sure they'll fill you in on Carnival's casinos.
Yes, "Diamond Jim" has been on a roll the last few cruises.
To the OP; Yes you can use your Sail & Sign card or cash. Now the machines don't drop coins anymore (except on rare occasions), it goes on your Player's Bank. So you will need to have your S & S card in the machine to transfer money from the machine to your Player's Bank. You set this up with a PIN number. You can cash out your Player's Bank at the cage. I'll leave the table tips and info to Diamond Jim.