Its my opinion that you shouldn't spend a lot of money when you first take up cycling. When I got back into cycling I didn't even know enough about the different kinds of bike to know what questions I should be asking my LBS. They kept steering me towards hybrids never once suggesting a bike with drop bars. As it stands now a hybrid would have no place in my collection of bikes as it wouldn't have been significantly different than my rigid mountain bike. I've seen so many new riders show up at our club rides with $600 comfort bikes that end up not being what they really wanted, and the following year they end up buying another bike that better suits them.
I ended up keeping my old rigid 21 speed mountain bike and have since put another 11,000 km on it. The money I would have spent on a new commuter went to my recreational bikes instead (which also serve as commuters).
I'd suggest a used LBS brand rigid mountain bike, rack, fenders, bar ends and some slicks. Something with decent quality components that is at least tuneable. Plenty of people have bought bikes only to use them a few times then sit in their garage for a decade. Let their loss be your gain. And if you aren't so diligent about ensuring it is properly locked, it will be a smaller loss.
Try and find a casual group ride as they usually attract a wide variety of bikes. Take a look at what's there and ask different people about their bikes. Then you can decide whether you want a higher quality hybrid, cross, road, touring, city, .... bike.