while the above is not exactly in LA (and neither is one of the below) a few other places that ,may be of interest are
Los Angeles International Airport Link for picture:http://tlc.howstuffworks.com/family/los-angeles-city-guide1.htm
Both interesting looking and an interestingly appropriate or inappropriate location, having good access for air to ground interaction, plenty of material (near the airport) and space (in the landing/takeoff area) Time pressure (planes in the air cannot land and are burning fuel), and other good and bad things.
A music concert hall: picture and imagine the reaction if in the middle of a concert (especially a cover of one of Elvis Presley's pieces an alien spaceship* appears, comes to hover over location.http://discoverlosangeles.com/play/arts-music-and-entertainment/los-angeles-music-festivals.html
Things of note: only good mid concert: large number of Civillians, Laser lights may make detecting energy weapon fire difficult (for both sides), Sound (if going) may cause confusion, plenty of electricity.
Disneyland: very close* in Anaheim.
(just search "disneyland" or "Disney Land" in the images sub-search)
Things: a number of attractions the part can interact with, before, during and after the attack; roller coasters, a castle, crowds of children, Food stands, fireworks (in the evening)-- your party will have access to all kinds of things for any shenanigans, up to and including a lake and a mechanical dragon. Biggest drawback is differentiating the supers from those dressed like supers or characters, but not as bad as a convention for that. Also damages: Disney may offer a deal of sue [the players] damages or allow them some ability to (if no one was injured) do some damage control and use [the players] images.