I did a short Spanish course for the last few months and found that fun and easy to fit in around my PhD, and my girlfriend completed a GCSE in Spanish whilst doing her doctorate so in terms of "will I have time" then I'd say that yes you would.
Having had a quick look at the web site describing the course and as an outsider to the university I would say that you should do it solely if it is something you're interested in. As a qualification I doubt it will be seen as much use by anyone who is not an alumni of the university, or unless you're subject area is closely linked. Therefore I would see it as an 'extra curricular' thing, similar to say doing a basic language course or taking a cookery or short basic history course. That is, if you enjoy it or think it would be interesting then do it, but if you're looking for a qualification that's worthwhile, perhaps do something else with your spare time.
As I say, this is just an outsiders view (though I guess most employers will be outsiders too), perhaps a view point from someone who's done it would be worth considering too if you can find someone.