UPDATE:
I have finished the wiring, and currently have a problem with the x10 signal from the house to the garage. The signal is able to reach the garage from my house, but when I turn on the garage interior lights (which are several flourescent fixtures), I guess this puts too much interference on the line because I am no longer able to control the fixtures from a remote. I have to go out and turn the lights off manually at the switch for them to work again. I am able to operate the exterior flood lights (500w halogen) with no problems, and I am also able to operate everything remotely if the remote is plugged into an outlet in the garage. But if I hit the switch for the flourescents from the house, that is all she wrote.
One option is, obviously, to not operate the interior lights on x10, because the exterior lights will probably be the most used anyway. I wondered if there was a quick and easy solution, because there may be times when I forget to turn off a light and won't feel like walking back out there.