RF Transmitter Receiver Recommendation?

[ScaleRobotics]

Update rate 6 readings/ second (all 6 sensors in 1 second).

That sounds like all six in one second.....

One of the XBee modules like this: http://www.sparkfun.com/products/8664
fits the distance, legalities, and timing specs. It's only $19.00 at DigiKey.com, and is highly configurable.