Pros:
Location: Immediately off the 101 freeway in San Jose. Impossible to get lost - you get off the freeway heading east and park your car. You're there.
Design: As other reviewers have mentioned, the people who designed (and maintain) this course have taken quite a bit of pride and show a true commitment to presenting an excellent DG experience in a parcel of land that would otherwise go to waste. For a 9-hole course, you'll need a good variety of shots to do well here and you'll also need to know how to play the wind and elevation changes as well.
That said, most of the holes seem to be designed for the 325-350 - foot thrower, which means that for noodle arms like me, par is a definite challenge. On the other hand, big arms can use the challenges posed by the terrain and trees to work on their short game while n00bs can simply use the short tees and have fun their first time out.
Amenities: Benches and bag holders at each tee, exceedingly well-designed signage (see the pix), actual stairs with railings that help going up and down the hills, especially when it's wet. Long and short tees, multiple pin placements, and a practice basket woo hoo!
Cons:
No drinking water on site. Keep this in mind if you're playing in the summertime when the temps get up near 100.
Constant traffic hum from the freeway. You get used to it, but it's definitely a "con" if you're after a back-to-nature experience.
Some poison oak, easy to avoid if you use basic precautions.
Other Thoughts:
The terrain here is typical for California coastal hills. Brown in the summer, green when it rains. Lots of slopes offering dangerous roll-aways if your disc lands wrong. Some trees are forgiving, others will grab your disc and hold on for dear life.
All in all, Hellyer is a deceptively good course that delivers much more than it promises. Baz says, "Check it out!"