I am brand new to biking. I actually am a runner who is currently training for the Toronto marathon and for part of my training I have decided to bike. Anyway the reason I am posting is because I would like more expert opinions than my own on what bike I should get. I understand that it is probably the best idea to get a used bike off of craigslist or something of those sorts. I know this general question has been posted before and I have done some research on craigslist and found this . . .

http://philadelphia.craigslist.org/bik/747654599.html

Is this a good bike for my price range? (Not much more than $300)