I would suggest that it depends on the location and type of business. Bartenders, servers, line cooks etc. are always looking for work - for some reason the industry turnover is huge. If you're in a trendy area where there's lots of food outlets, word-of-mouth will take you a long way. The sign on the window might even be overkill - unless you want one that says 'No Help Wanted' to keep out the riffraff...
Then again, if it's a shawarma place in the suburbs...