i would say, if you can afford the insurance and whatnot then yeah definately.
makes life a hell of a lot easier and getting out of campus regularly will keep you sane (well kinda anyways) plus petrol is cheap as chips down in gibraltar, as is alcohol and smokes if you're that way orientated.
there is a minibus for the use of the students though at reasonable rates and there are a few bikes kicking around the place.
do keep in mind though that the roads are full of spanish drivers which are the equivalent of 80'yr old blind people who have drunk a bottle of whiskey and are on the phone whilst fiddling with the stereo and putting on their makeup.