I will have one day in Palo Alto free on a business trip but will not have a car. Any ideas on sights to see by walking or a tour?

You can easily walk around "downtown" Palo Alto and over to Stanford's campus on University to Palm Drive. If you're a good walker you can then get over to the Stanford Shopping Center. Since I live here, don't know about tours and always have my car, but I think there are bike rental places and there's a shuttle bus from Stanford called the Marguerite--try doing a search. I don't think you have to be a Stanford employee to use it but not sure. The new art gallery is open on campus now but has strange hours so be sure to check. Lots of really good little restaurants in Palo Alto. Enjoy.