1) What do you consider to be long range, medium range and short range in TKD, and particularly sparring, since TKD is rarely practiced with grappling in sparring?
Long range - side kick can make contact
Medium range - punch can make contact
Short range - knee can make contact
From what I've observed (WTF):
Long range - not within hitting range (need to do a step side kick etc. to actually make a hit)
Medium range - can make kicking contact without stepping forward
Short range - punch/back fist can make contact
Most TKD fighters rarely fight "short range" (by my definition). I'm inclined to agree that TKD is a long range art - take the opponent out before they can stab you in the stomach :P
2) Where do you prefer to fight?
Medium range, I've taken to a Muay Thai meets TKD sort of sparing style myself as the school I first started training at was a hybrid of the two arts under the title TKD (no WTF or ITF affiliation)
3) From the people you train with and your perception of the art, where would you say TKD's best fighting range is?
As I said, I find it to be most effective somewhere between (by my definition) long and medium range. A TKD kick done properly can take you out easily. (Of course not to say TKD is only about the kicks)