For that distance,and those roads,I'd go with a hybrid or maybe even a MTB with slicks. Kona's Dew series,Trek's Soho's,Specialized Crosstrails or Globes. Something that won't beat you up and will have low enough gearing to get you up the hills easily until you build up your legs,yet tall enough for you to get some speed once they are. If the flat bar doesn't do it for you,a trekking bar will give you plenty of hand positions,let you tuck in aero,and will only be about a $30 upgrade for bar and tape(all stock controls will swap over).