Allow me to clarify -- Google Maps is a great tool for rough planning, because it's (a) easy to use and (b) has satellite imagery and streetview, that allow you to check the roads in advance. The pictures below - the first one is a good road to bike on (it used to be part of my commuting route), the second is lousy to ride on, particularly during rush hour. Where StreetView isn't available, you can use satellite imagery to look for shoulders.

This thread has links to more tools you can use, and gets into how to eke out altitude data from Google Maps.