The Palo Alto Baylands Preserve is a flat mostly unpaved 5 mile loop trail. Leashed dogs are allowed, unless posted in special bird nesting areas. There are several entrance points. One of the main starting points is from Hwy 101 heading north, exit San Antonio Road and turn right. San Antonio Road will bring you directly into the start of the Preserve. Please note that there is an adjacent park on the right which is a City of Mountain View park that does not allow dogs. However, no need to worry, the dog-friendly Palo Alto side has plenty of trails for you and your pooch to walk or run.