San Mateo is located south of San Francisco, and is one of the larger suburbs in the Bay area. It has a population of about 97,000 people. The city has vestiges of its former life as a summer home locale for the wealthy from San Francisco with some of the old mansion still standing.
Downtown San Mateo and the area surrounding S El Camino Real are relatively walkable, but most every day errands will requires a car. CalTrain offers train service to nearby San Francisco, and from there you can easily transfer to the BART network making most of the Bay Area accessible from San Mateo.