If you are coming from farther away, it's best to rent a car or take a taxi/rideshare to Agoura Hills. Once you get there, you can easily navigate by car or by foot. Parking varies depending on location but at most, it would only cost a few dollars for the day.
If you have more time, consider visiting the beaches in Malibu or taking a scenic drive on Mulholland Drive. If you have less time, skip Peter Strauss Ranch and add a visit to the Calabasas Farmers Market where you can explore a variety of local vendors and experience the flavors of the region in one place.