Marijuana may be legal in California now, and this year's Coachella may fall on stoner holiday 4/20, but that doesn't mean that the festival's organizers are cool with you just lighting up in plain sight. The fest is held on private property, and per the FAQ page on Coachella.com: "Sorry bro. Marijuana or marijuana products aren't allowed inside the Coachella Valley Music And Arts Festival. Even in 2018 and beyond. If that changes we will update this answer."
TMZ reports that the city of Indio, where Coachella is held, still doesn't allow selling, cultivating, or distributing weed or smoking it in the open, although by state law, possessing a small amount for personal use is acceptable. They also helpfully point out that neighboring cities like Palm Springs, Cathedral City, and Desert Hot Springs are all 420-friendly, so, uh, keep that in mind if you're looking to score some legal bud.
