What I would recommend for you is do a bit of research about a few brands, like Trek, Specialized, Giant, Fuji and GT and find some local dealers. Go in knowing what bikes you want to look at and ask to ride them, you should have no problem getting test rides. After you ride a selection of bikes, go home and make a list of things you liked about each bike and a list of things you didn't like. Usually, there are one or two bikes that really stick out and then go ride them again.
Once you make your decision go in and see if the shop will negotiate on prices; some will, some wont. If they do negotiate, they will have a low end retail price that they wont go below, and its usually around 10-15% lower than the advertised retail price depending on how big the shop is. The bigger the shop, the lower their prices. Push them a little bit (its like buying a car) and you will usually have no problems saving some bucks.