For 2.5 miles you could just as easily commute on a chopper or penny farthing I'd look for a second-hand mountain bike without suspension. Lots of people tend to buy these, ride them a few times, then leave them forgotten in the garage until they discover it and decide to sell it. The upright geometry and ability to mount fenders, lights and a luggage rack make them ideal entry-level commuters, usually needing just a tune up and a change to slick tyres for riding on the road. If you really decide you don't like cycling (not everyone does) then consider walking to work.