Also when you say 30Khz is that the i2c clock frequency?
That's the clock frequency of the high speed I2C in ROBOTC. ~10KHz is the standard speed.
Do you know if all of the sensors will work at that speed?
Not all sensors. Most HT sensors are only certified at slow I2C speeds but quite a number of them will also work at the higher speed. All of the Mindsensors ones work fine at 30KHz. The US sensor doesn't work at all at 30KHz.
Do they allow each port to run at a different speed?
Yeah, you can configure each sensor port at different speeds.