Having spent quite a bit of time in the Santa Cruz mountains, Big Basin SP, Pescadero/Butano SP, and Portola Redwoods SP areas, the no mosquitoes thing is a bit optimistic.
Sure it's not as bad as say, northern Minnesota, but once you get away from the ocean and desert areas, if there's standing freshwater around there can be plenty of mosquitoes. The last time I camped in Big Basin everyone was running through clouds of them to/from the restrooms.
But yeah, in the cities like SF and LA, there aren't very many. The city would spray for mosquitoes at night when I lived in San Mateo, which surprised me coming from the midwest and not expecting Californians to be ok with such chemicals sprayed throughout their neighborhoods while they slept.
In my part of Marin County, they use a bacteria, Bacillus thuringiensis, to control the mosquitoes. There are enough mosquitoes so that you'll get bit if sit in one spot long enough, but I don't recall ever getting bit while walking.
Sure it's not as bad as say, northern Minnesota, but once you get away from the ocean and desert areas, if there's standing freshwater around there can be plenty of mosquitoes. The last time I camped in Big Basin everyone was running through clouds of them to/from the restrooms.
But yeah, in the cities like SF and LA, there aren't very many. The city would spray for mosquitoes at night when I lived in San Mateo, which surprised me coming from the midwest and not expecting Californians to be ok with such chemicals sprayed throughout their neighborhoods while they slept.