Welcome To Bike Forums, IHavenI!

With a $300 budget, buying a new road bike is most likely not an option. However, since you do live in the SF bay area, you do have several other options. They are as follows:

1) Join the Bike Kitchen, a bicycle co-op, located at 650 H Florida near 18th street. Monitor the SF Craigslist for an old used 80's styled ten speed road bike. Once you've located a bike, take someone with you who "knows bikes". That will be your "expert". Have your expert accompany you and inspect the bike, both before and after you test ride it for at least twenty minutes. They should be able to tell you something definitive about the bicycle's overall condition and its fit. If you don't feel 100% comfortable riding the bike, then don't buy it! If you suspect that it's too large, it most probably is, and again, don't buy it!

Once you've purchased your bike, the Bike Kitchen should be able to assist you in making any upgrades, adjustments, installations, or repairs.

2) Once you've joined the Bike Kitchen co-op, they can assist you in your quest for the proper frame that can accommodate your size. Sometimes you have to be patient and wait for the proper frame to surface.
Otherwise, you can locate a frame independently, thru Craigslist, a yardsale, or perhaps a purchase online.
The Bike Kitchen will have used components. Some of these components will most likely fit your bike. You can therefore, build your bike right there at the co-op, under the watchful eyes of seasoned veteran bicycle mechanics.

3) You can purchase a road bike online and complete your build at the Bike Kitchen. The following slightly over budget online bike, just might be of some interest to you:

The Motobecane Mirage ~ $330
www.bikesdirect.com/products/motobecane/mirage_xi_steel.htm

4) You can slightly increase you budget and buy either of the following hybrids at a local bicycle shop:

a) The Giant Cypress.st ~ $350
www.giant-bicycles.com/en-us/bikes/model/cypress.st/9019/48871/

b) The Giant Sedona.st ~ $350
www.giant-bicycles.com/en-us/bikes/model/sedona.st/9025/48885/

* Option #3 will require a few immediate high priority inspections. Make certain that the bottom bracket has been properly lubricated. Also have one of the co-op mechanics inspect the brakes, derailleurs, and shifters. Plan on upgrading your entire drivetrain to Tiagra or Sora, by next summer.