I initially purchased a comfort bike (700c), but the limited gears for the hills around me made that a chore.
I did got a Schwinn Varsity road bike (700c), but the tires kept getting flats.
Both of these bikes were from Walmart.
I ended up taking both back and getting a Giant Escape 2 Hybrid (700c) and love it. The tires are bigger than the road and have more thread to fight off flats, but are smaller than a mountain bike's tires.
I have gotten a flat, but I ran over a commercial box staple.
I recommend the hybrid.