Yes, with the current (Ver 1.0.5 and later) video firmware, you can set your tablet’s fans to Auto (Default) or Low* fan speeds.
To access control of the fans speed, first update to the latest firmware by opening the Wacom Desktop Center. Select the updates menu and follow the instructions to update your Cintiq firmware. Do not disconnect your tablet, allow the computer to go to sleep or shut down the computer during the firmware update.
When the update is complete, again open the Wacom Desktop Center, select the Cintiq Pro 24, and choose Display Settings. This may take several moments to open. Once the settings window has opened, click the advanced button. New fan controls will be located in this window and allow you to choose Auto and Low for the fans speed.
*Note decreasing the fan speed to low may cause a temperature increase on the surface of the tablet.