Sorry, but we know of no one in your area who we can recommend for a room addition. Call the National Association of the Remodeling Industry (NARI) in San Francisco. Hopefully someone there can refer you to a NARI member who works in the San Carlos area.
Regardless of which contractor you select make sure to do your homework. Check with the California Contractor's State License Board to insure that the contractor's license is current and in good standing. Also, get a loan application form from your bank and have the prospective contractor fill it out. Use the information he provides on that form to thoroughly check his references.
If the contractor is reluctant to give you this information he may have something to hide, and you should steer clear of him.