You can get the floor plan information from the Town of Los Altos Hills Planning Department. They will have microfiche of all of the homes built in the community. Because the Town is comprised of mostly custom homes, your chances are far greater that a lengthy and detailed file exists in the Town's records of the home's plan.
As for interior remodeling, some of the homeowners get permits and some do not. If the exterior is being modified, most assuredly, there will be some permits. However, if the remodeling was limited to interior amenities without changing the footprint of the home, there may not be any permits on the interior changes. A good contractor, however, should be able to help you assess the changes in the home and if these changes will require modifications to meet current building codes.
Please keep in mind that while you'll be able to view the plans on microfiche at the Town Hall, you will NOT be able to get copies of any home plans without the express written consent of the architect. All plans are the work product of an architect, and the architect must release the plans to you if you want a set.
Good luck! And work with a great Realtor to help you purchase your new home!!
Area Pro Realty-People's Choice
Los Altos: http://www.losaltoshills.ca.gov/building-and-planning
Additionally, do a thorough home inspection conducted by a competent inspector.
Are you purchasing a foreclosure that has been remodeled? Wanting to make sure the work was done correctly? I would suggest going to the county to suggest permit information. I am not sure how they do that in California. A lot of counties now have everything online. I hope that helps!