Look at good hybrid bikes in the $600-$1,000 range. I recommend a hybrid for several reasons: 1. You will ride a bit higher and thus be a bit more visible to drivers. This posture will also give YOU greater visibility. 2. A flat bar shifting and braking lever system is better when biking in traffic (unless you're a highly experienced and highly skilled rider). This is because the controls are literally at your fingertips. If you ride a drop bar, you'll probably be on the tops much of the time making the shifters and brakes just out of reach. 3. A flat bar accommodates a mirror better than a drop bar. A good mirror mounted at the end of your flat bar gives you very good vision of what's behind you. This is essential when you take the lane or change lanes. 4. A hybrid will give you greater choice in tire sizes. Depending on the season, you will want to go with a smooth 28 to a 35 with with treads. 5. A hybrid frame is more likely to give you dropouts for racks.

Good luck.