>>392751Personally? Get a dirt bike. I'm not a fan of quads or the riders they attract.
They've got their applications, especially when it comes to utility... but offroad out here, go with two wheels. Can't really say about LA mud though, never been there (and don't really have any desire to). I'll take high altitude dirt over mud any day of the week.
Spend some money on gear first... helmet, boots, gloves, goggles, etc; use what's left to buy the vehicle.
If you're decent with a wrench, pick up something off craigslist that needs some work for cheap.
If you're not mechanically inclined, find a brand that's got decent dealer support in your area and go with that.