Start by checking some basics: Your speedometer, stop lamps and horn should all work, prior to trying to further diagnose the problem. Do they?
Check fuses 42 and 53 in the passenger compartment fuse panel if your car was built before 11/2004
Check fuse 29 in the engine fuse panel if the car was built after 11/2004
Or look in your owner's manual for a "speed control" fuse location.