The freqs I posted above are all analog in the civilian AM Aircraft band. Just about any scanner should be able to receive.
In previous years, LA City Fire would do a water drop demonstration. They would be on LA City Air Ops 119.975 and maybe their Air/ground at 154.830 (FM).
If you're at the event, the Airboss channel can give you an early warning if one of the rotors needs to depart for a call. They'll usually clear the field of all spectators before they lift off.
The best bet would be to bring a P25 capable scanner with close call capable of monitoring military and civilian air band, like an old BCD396XT would work.