An intercooler is basically a radiator for air. It cools the air charge before it enters the engine, to remove some of the heat which has been added to it via compression (supercharger or turbocharger). Granted, in front of the radiator isn't the first choice, but sometimes you don't have much choice. As long as the cooling system can compensate for the lack of airflow through the radiator, it should be OK. (Some factory turbo cars are designed this way.) But yeah, if you have the option, the best place to mount the intercooler is somewhere with good cooling airflow.