i'm looking at getting a bike pretty soon. i'm not sure if i want a mountain bike, or a road bike. my main use will be riding to the beach, which is about 6 miles away i think. i ride in the canal, so it's pretty flat, except for the street underpasses. what do you guys suggest? there's some decent looking cheap ones on craigslist in my area, but i don't really know anything about bikes.