San Diego Co. is lovely by the coast, nice weather and warm, but mild weather. But, the traffic is crap, especially in the summer during the Del Mar Fair and then the horse racing season. Be prepared to drive. Unless you live/work near the coaster (commuter train) and/or trolley lines the public transport is lacking.
If you live inland it can get really hot and in the winter really cold (well for Californians!) The traffic tends to be a bit better on inland freeways, but not much and it may have gotten worse since I last lived there.
Lots of houses and apartments don't have air con, especially if they're pre-80s. Lots of bungalows and condos, but also a mix of larger homes and apartment complexes. It really depends on what area you would be living in.
It's nice because it is close to everything: the ocean, deserts, mountains, Mexico. You could enjoy the beach and the snow in one day if you wanted to!
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Renting is expensive, it might have changed with the housing bust, but I'm not sure. Do some web searches and you'll probably get a good idea, the further inland you go the cheaper it tends to be (but not always).
If you have any more questions ask away!
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