Seems like each year the Hollywood Bowl hosts more and more non-Los Angeles Philharmonic-produced events (dubbed lease events).  The theater policies are different (more strict) for lease events.  Here are the official Leave Event Theater Policies from the Hollywood Bowl website.

Not Permissible in the Theatre during Lease Events:

• Alcohol and/or controlled substances. You may purchase alcohol inside.
• Umbrellas and chairs.
• Cameras, audio, and video recording equipment.
• Glass (including drinking glasses) and aluminum cans, regardless of content.

The following are allowable in the Bowl:

• Picnic baskets and coolers no larger than 15″ by 22″ long by 15″ high.
• Factory sealed non-alcoholic plastic bottles, one liter in size or less.
• Re-useable containers (such as Tupperware or sipper bottles) holding food or non-alcoholic beverages.
• Blankets or seat cushions.