Menlo Park sits on the San Francisco Peninsula between San Jose and San Francisco, about 30 miles south of the city.
Caltrain runs frequently between San Francisco's 4th and King station and San Jose Diridon, stopping at Menlo Park station on El Camino Real. The journey from San Francisco takes about 40 minutes on a baby bullet express; local trains take around 55 minutes. From San Jose the trip is about 30 minutes. Caltrain is the simplest way to arrive from either end of the peninsula without a car.
By car, US-101 runs along the bay side and Highway 82 (El Camino Real) runs through the city. From San Francisco, US-101 south to the Willow Road exit puts you near the Meta campus; the University Avenue exit from 101 puts you near downtown. Parking in the downtown area around the station is metered but usually available.
San Francisco International Airport (SFO) is about 12 miles north; a rental car is the most practical option for that connection unless you're going directly to the Caltrain station at Millbrae.