QUESTION: 
Since the rover is remotely controlled, how long would it take the
commands from Earth to reach the rover? What's to stop the Rover from
driving off a cliff during the delay?

ANSWER from Jack Farmer on November 20, 1996:
The time delays between signal commands will depend on where Mars is in
its orbit. I think the upcoming missions are planning on 10 minutes or so
per command cycle. 

ANSWER from David Dubov:
The 'round-trip' light time from earth to Mars is approximately 20 minutes
at the time Pathfinder lands on the surface of Mars. Processing delays at
the rover, at the lander and on Earth add time between a command request and
telemetry response.

Recognizing that this delay would not allow ground operators at Earth to
control the rover in 'real-time' on Mars, the designers of the 'Sojourner'
rover included an on-board hazard detection and avoidance system, a
navigation system and fault protection software to protect the rover during
traverses. The hazard detection system (a combination of laser-ranging and
imaging along with tilt, turn and vehicle configuration sensors) allows the
rover to autonomously detect obstacles in its path and turn to avoid them.
The navigation system on-board the rover monitors the avoidance maneuver,
eventually directing the rover to complete its commanded traverse after the
rover has driven past the obstacle. The fault protection software monitors
the vehicle state (e.g., power generation, thermal control) to ensure that
no other condition prevents the vehicle from safely completing its traverse.