I guess it depends a lot on the kind of work you're doing - if you're busking on the street, chances are you'll be doing that during the day (when all the tourists are about), so you probably won't get to see much. If you're working in a pub or restaurant, you might be working more nights, and would still have a chance to sightsee during the day.
If you're really interested in seeing things, it's probably not a bad idea to save up as much as you can in advance so that you have the freedom to go as you please. Unless you are legal to work in the EU, you probably won't be making a ton at whatever job you can find, so you'll probably have to stay put quite a while to earn enough to pay your way home.