During the summer you get the marine layer causing difficulties, but it should be over by now. Smog and haze in the LA Basin can cause problems at any time really, especially when the sun is low over the Pacific and you are flying towards the west. Reported conditions can be VFR but you cannot see a thing, if you get the drift.
If you are there for a week hour-building, why would you want to stay around somewhere like LA? There are plenty of far nicer places to go. Head north towards San Francisco, and/or into the deserts towards Vegas, Grand Canyon, Phoenix and back via Palm Springs or San Diego. Make a proper holiday of it!