I would not worry about a carbon fork, it's seems that 99% of the new bikes have them anyway. Some people are concerned with carbon steer tubes (the upper part of the fork), as these can be damaged if the stem is overly tightened. However, carbon steer tubes are only on very high end racing bikes. Most carbon forks use alloy steer tubes.

We just replaced the steel fork on our tandem with a carbon this year. Lighter weight, and very nice ride.

Another option if you feel you must have a steel fork would be go custom. Waterford makes very light steel bikes that can be spec'd with carbon or steel forks. However, you are looking at more then $2000 for just the frame.