I would definitely go the road bike route then. Should you decide you want to ride around on the trails when you move, you can always get a mountain bike.
You can definately get a quality entry level road bike for under a grand. Given that you are going to be putting in at least 20 miles a day, I would try and get something that had Shimano 105 components. Where do you live? I would go down to a local bike shop and tell them you are interested in getting a road bike and see what they have, have them tell you what size frame you need (this is done pretty easily by having you stand over a bike). Then I would check out ebay as you can find some pretty good deals on bikes there, and you can get a lot more bang for your buck on a used road bike. If you decide you want a new one, specialized, trek, and fuji make some decent cheaper entry level rides. Stay away from brands like cannondale, giant, and anything european (good bikes, just not high in the value department).
Also when you are looking at prices, dont forget to factor in what you are going to spend on accesories. If you are going to be commuting anywhere near dawn or dusk, a headlamp and a blinky is a MUST HAVE. Also all the little [censored] adds up, saddle bag (you need a way to carry your spare tube and patch kit), a frame pump (try and stay away from CO2 pumps), water bottle cages and water bottles, get a helmet, and a pair of those sexy ass lycra shorts. I would also recommend getting tire liners and tubes that have slime in them. Also a decent bike is going to have "clipless" pedals on it, so you are going to need a pair of shoes. It sounds like a lot, and it adds up, which is why its important to keep it in mind when deciding how much to spend on a bike so you dont go over your budget. But stuff like helmets and shoes vary in price. dont let anyone talk you into any of the expensive ones, when you are just starting out you arent going to know notice any perfomance gain, and a $30 helmet will protect your head just as a well as a $200 helmet (they both meet the exact same crash standards). And all the other stuff can be had pretty cheaply. You can even try haggle and if you buy a bike get them to throw in bottles and cages, or cut you a discount on your other purchases. Also check out
performance, its a mail order place. They are usualy much cheaper on stuff than your Local bike shop