I'd say go to a few bike shops, see what they have. Ask about used. Department store bikes are too low quality and a waste of money. A decent new bike will run you about $500. For that you will get a hardtail with a spring fork. It will have disk brakes, probably hydraulic. Reasonable components and should last you for years unless you really get into it and want to upgrade. Stay away from cheap full suspension. I personally really enjoy it and have worked up to a Trek Fuel EX7 - full suspension 'trail' bike. I ride about 2,000 miles per year. Mt. Bikes are how I stay in shape for fall.
