Welcome To Bike Forums, Smarties!
If you have hills to climb, you'd be better off by avoiding a single speed. However, a single speed would be the best solution for a college student with a budget of $300 and only had a flat terrain to traverse. You could purchase a brand new chromoly steel single speed and get a warranty.
Of course, the best route to take, would be to monitor your Craigslist and look for an old 80's styled 10 speed road bike. You should have someone accompany you who "knows bikes". That will be your expert. Have your expert inspect your bike, both before and after your twenty minute test ride, before you seal the deal with a cash exchange. Your expert should be responsible for informing you about the overall condition of the bike and whether or not the bike looks like it's a good fit for you or not.
You should join a nearby bicycle co-op, as soon as possible. The co-op leaders and mechanics can assist you in locating a bicycle frame, upon which you can build with the available components at the co-op. If you're patient, eventually one should surface, if you have a thriving co-op.
Besides using the local Craigslist and the co-op as resources for locating a bicycle or frame, you should also check local yard sales, eBay, and second hand stores. You can also purchase a frame online and build it up at the local bicycle co-op. Your goal should be to locate a used chromoly steel bike in fair to excellent condition. If you can't locate a complete bicycle, then your expert should be able to advise you about the details of obtaining the proper frame.
You might also purchase an entire bicycle online and complete the assembly at the bicycle co-op.
The following bicycles may be of some interest to you:
1) The Dawes Eclipse 1 ~ $260
www.bikesdirect.com/products/dawes/eclipse1.htm
2) The Gravity Dutch ~ $250
www.bikesdirect.com/products/gravity/grav_dutch_xii.htm
3) The Trekking Bike ~ $300
www.bikesdirect.com/products/clearance/trekkingbikes.htm
Of course, OTOH, if you could slightly increase your budget and secure your best bet with a Giant bicycle dealership. You could then get properly fitted and purchase one of the following chromoly steel bicycles:
1) The Giant Boulder ~ $360
www.giant-bicycles.com/en-us/bikes/model/boulder.w/9043/48966/
2) The Giant Sedona ~ $350
www.giant-bicycles.com/en-us/bikes/model/sedona.st/9025/48885/
3) The Giant Cypress ~ $350
www.giant-bicycles.com/en-us/bikes/model/cypress.st/9019/48871/
Good Luck!
