I'm looking for a bike for exercise and general riding. I've narrowed it down to three choices, and wondered if anyone has input or suggestions.
Diamondback Wildwood Deluxe $335
Jamis Explorer 2.0 $400
GT Nomad $400
It is difficult for someone to suggest a bike for you. At a given price point, bikes tend to be very similar in quality. A bike with wider tires (1.5 inches wide or 35mm wide) enables you to ride on both pavement and on typical urban park trails, so it is a good choice for a bike that will be used for fitness, recreation, and commuting.
Owning a bike is more fun if the bike is kept in good shape. Buying from a shop that is just a few blocks from your home makes it easier to get the brakes and shifting adjusted from time to time, and to keep your bike in shape. Start by visiting the shop closest to your home and test riding the bikes in your price range. Let the folks at the shop know how you plan to use the bike and where you plan to ride.