The Rancho Potrero Open Space area is located in Newbury Park off of Lynn Road, just east of the intersection with Rancho Dos Vientos. The area includes an equestrian center where Rocking K Horse Rentals is located and is adjacent to the Rancho Sierra Vista/Satwiwa area in the Santa Monica Mountains National Recreation Area.
A new parking lot and restrooms was built in 2015 allowing for easier access to the Rancho Potrero Open Space (although notably the parking lot closes at 4pm, well before sunset). It is accessible just west of Rocking K off of Lynn/Potrero Road.
There is a trailhead further west of the parking lot, just before Potrero (Lynn) Road takes a sharp right turn. You can usually find parking off pavement here. A short (1/4 mile) walk up the hill gets you pretty darn nice views looking towards Camarillo and the Channel Islands. Take the adjoining trail east towards Rancho Sierra Vista and the Satwiwa Native American Indian Cultural Center.