I +1 the statements so far about fixed gear so far.

Look used, you should be able to find something. For someone 6', a MTB size of 19-21" and Road bike size of 56 to 58cm would be about right (+/- 2 range). Check out Craigslsit, coops, auctions, pawn shops, garage sales, and LBS that sell used.

The mid 80's to early 90's rigid MTB's made excellent all around bikes. Beefy frames, ability to fit wide tires, and stable geometry made them very versatile. Many also came with eyelets for racks and/or fenders.