Where in the OC are you located? There are always great deals popping up on craigslist. As stated above, know your size and have money to go right away! I have scored amazing deals by replying and buying the same day a bike is listed. I have also kicked myself for waiting and missing out. Decide if you are wanting a bike that is ready to ride or might need some basic maintenance. You will save money if you are willing to clean a messy bike and replace simple things like tires/tubes, cables/housing, bar tape, and maybe brake hoods. I have scored several great Centurion Ironman bikes for sub $175, but they needed around $50 in updates/repairs. One that has been "tuned" will cost you more and may end up needing the same repairs/updates.

I would think in your price range, you will likely end up getting the most bang for your buck with 80's Japanese bikes. Centurion, Miyata, Nishiki, Univega, etc.

Is 58cm your size? If this bike was my size, it would be in in my garage Rare! Centurion Prestige Full Dura Ace Road bike for sale!!!

If you are taller and more around 60cm, I might know where you can get a good deal on a miami vice centurion ironman

If you want to buy from a shop, The Bicycle Stand down in Long beach sells older used bikes. Their prices are higher than I would pay, but they include an basic overhaul with purchase.