Pros:
First off, there aren't many disc golf courses in Rancho Cucamonga--so as a resident of the city, having Glen Helen to play at is a great benefactor. The course has many strengths, and it's great to play with friends, or practice alone. There are 18 holes with tees on each hole, and it has a great flow. A couple holes will challenge experienced players, especially on windy days. Hole 7 is especially fun and challenging since the altitude of the tee is much higher than the basket. This is a really fun course to experiment with as well. Many holes can be approached in many different ways since obstacles aren't too extreme. Glen Helen is a dafe disc golf course to play, and I don;t imagine myself losing a disc here, but you can overthrow the 19th hole and end up in a small lake.
Cons:
There is a $7-$10 parking fee, depending on whether or not you play on the weekend, but unless you play alone, I don't consider this a big downer or deal-breaker.
It can get VERY windy, and even if you check the weather, the wind is hard to predict. The wind makes some holes extremely difficult to par on.
Other than that, I don't see any downfalls for this course.
Other Thoughts:
Overall I love this course. It is extremely fun to play on, and I look forward to playing it in the future. If you're ever in the area, I'd say it is definitely worth checking out. It's a very peaceful area as well, making the atmosphere that much more attractive for disc golf. A very enjoyable course to play!