I can tell you that Greektown is the EASIEST to get to. Follow the signs for the tunnel for Canada (don't forget to stop by Winsor on the other side of the river - only $2 to get to Canada). And the casino is very close to the tunnel. You will see the signs for it.

As for the other two (MGM and Motor City), since I get lost crossing the street, I will leave that for others. You may want to jump onto Casino City and get the addresses then map them out on Mapquest.

I got to Greektown very easily and asked for directions to MGM from the parking attendant, then the same from MGM to Motor City.

Enjoyed all three, however see if you can schedule dinner time near the MGM. They have an EXCELLENT buffet.