pay attention to the source and direction. Beacon Park is actually north of the concentration of the Plume, and its moving in a Western Direction.
State regulations require remediation, but it is remediation to a particular level. The plume has created a huge superfund site because it affects all water well sites in Irvine, so they are pouring in millions to try to control it to prevent contamination. Mostly comes down to pumping through millions of gallons of water through filters to recover these organic compounds. Well contamination is probably a more pressing problem than VOCs a few hundred feet below you.
Other items are probably more realistically more hazardous such as living close to busy freeways where contamination is freely spewed into the air.
In general finding a place without an issue is going to be hard - many places in CA are/were superfund sites. The risk is always there, and as long as most people buy/don't care, then you'll just see values go up and up. I prefer open disclosure than hiding it, but its no different than the fact many businesses in CA have put up a sign saying that there are chemicals/substances around that could cause cancer. Around Celadon I saw Construction Signs saying if there were high winds that blew the dirt, they needed to call an emergency number (I feel for those workers, they will probably get more exposure than anyone living there after its all built up)- no doubt goes back to contamination from the old Base.
If you loved Opus I would still sign it. Its not like it'll sit there - they sell these units that aren't even built yet. FWIW, I have signed on a place at Rowland that will be rdy later this year, so clearly i've made the decision for myself.