I don't have a answer as to what / where is the least expensive parking for Tampa cruiseport, but I do know that the parking garage in the port area is, like, RIGHT THERE!. I believe it's around $15 per day, but, boy-o-boy is it convenient. You might check the port of Tampa's website, it may have some links to near by cruise parking. You could also try a general "Google" search. A quick, last minute cruise sounds like such a fun thing to be able to do . . . the best I can do is Mexico from San Diego or LA . . . sure would be nice to be able to have the option to drive to a port on short notice. Hope it works for you.