Nashbar and Performance has 700c tires cheap if you can wait a few days for them to arrive. Going 27" you'd be paying a lot more than just tires - probably more than you would if you had bought a couple of your LBS's $30 tires. Plus you do have the headache of making sure brakes and such work, clearance, all that jazz.

Best suggestion - get a pair of tires online from nashbar/performance/biketiresdirect/etc. You should be able to get a pair for less than $30 if you're really hurting for cash.