The San Francisco Bay Area is blessed with many open space preserves and hiking locations. You can search the website of the Midpeninsula Regional Open Space District to explore day-hiking spots. Below are some hiking spots that are within a 10-15 minute drive.
Sunnyvale, itself, is brimming with neighborhood city parks (often attached to elementary school locations, doubling as the 'playground area') such as Braly, Ponderosa, Fair Oaks, Lakewood, and many more.
Braly park, with a children's play area, horseshoe-throwing pits, shuffle boards, a sand volleyball court, a water play area, and lighted tennis courts, is a short walk away from the Charter Palms Townhomes and can be viewed over the drainage canal from the east side of the complex. The park is 5.6 acres and has several picnic sites.
Sunnyvale City Parks