There are two possible ways to delve into "Grizzly Park". You can either get annoyed and frustrated at how overall imbecilic and awful the movie film is, ... OR you can invite a few friends, open a few beers, and wallow in the numerous so-bad-it's-good qualities; - as there are: absurd plot, stereotype characters, cheesy gore, and some of the stupidest dialogues ever penned down.
Personally, I really like to believe the film nevertheless began as a serious and reasonably ambitious creature-feature, but that somewhere along the course of the project, everyone involved put their heads together and collectively decided: "screw this, let's go completely over-the-top instead". I even don't think writer/director Tom Skull really exists, but a sort of inside-joke alternative for Alan Smithee, or something. How else would you explain that "Grizzly Park" is the only thing on his resume?
The basic idea is okay. As part of their community service sanctions, eight juvenile delinquents must pick litter in a Californian National Park. There's an escaped serial killer at large in the area, and a big hungry grizzly bear on the prowl in the park, and still the intolerable & dim-witted teenagers manage to be their own worst enemies.
The regular assets of a creature-feature/slasher film like "Grizzly Park" are the gory kills and the guessing-game of which characters will die or survive. The killer grizzly obviously hates dreadful stereotypes and claws them mercilessly apart. Some of them don't stand a change for survival, like redneck Neo-Nazis or Latina drug-gang members, while others sign their own death certificates by claiming stuff like "old people are easy to steal from" or "sex with 15-year-old girls is the best kind". And, oh, love the silly bear song!