Ah, work abroad. The elusive magical being we're all chasing.
I would say that since you've only just graduated, you should check out BUNAC and maybe try to get a work visa. You'll be able to stay longer than the 3 months max for continental Europe (because of the Schengen agreement) and it will be much easier for you to find work because you'll be legal. Under the table jobs are available if you're willing to wash dishes or wait tables. Some people have said that bartending jobs are easy to come by but I really don't think so-- everybody and their dog wants to be a bartender so unless you have tons of experience you're probably assed out on that one.
And the reason there is no Spain / Greece rail pass is that the countries have to share a border. In other words, you'd need a rail pass with Spain, France, Italy and Greece if you wanted to do that. Unless you're planning to spend some time in France or Italy though, I would say you should check out RyanAir
and Easy Jet
for cheap airline tickets that you can book in Europe. Good luck!