To reach the cruise terminal at Port Rashid you can take a Taxi from Airport
or take the metro (from Terminal 1 or 3 direct access to the metro stations)
till ADCB metro station which is the next to enter the port.
If you have time till Check In you can stay in the metro untlil Jumeira and get same route
back to ADCB. Then you have a wonderfull view to the skyline of Dubai
Metro Ticket for 1 day is about 5 euro