Where I see sensors, I am good(with the exception of the one at the end of my road. I park on the sensor wire, but it never trips). There are several streets that I travel often that have no visable sensor wires. I try to guess where they are at, but usually fail.
Another option is to put your kickstand down when you stop at a light. Even if you can't see the sensors in the ground, they're there. The 250 has a horrible problem with its wheels not being magnetically strong enough to trip all sensors, and the engine is too high up for them also. The kickstand however is nice strong metal and will usually do the trick. Try that before buying the green brick. Just remember to watch the cross lights so you can lift the kickstand and get into gear when the light changes for you.