Another vote for Pimsleur. I have all 90 lessons of each French, German and Italian and find them very useful. I also first looked on eBay. There are a few people on there who are dealers who might have Greek for a reasonable price. You might check your library too. Mine has many of the 8-lesson traveler sets.

I've learned a bit of Greek although I find most Greeks talk to me in English. Though knowing how to say, Where is ..., has been helpful.