In Texas, the deadline is 30 days from the time you move here to when you have to register. Of course, if the cops become stretched too thin here as in other places, I'm betting people will get away with it. My brother in law got hit at a 4 way stop - not his fault, and the cops told them straight up they wouldn't come out for a report unless someone was injured or the vehicles weren't driveable. So it might be poetic that we're getting a bunch of Californians coming here.
Still, I see a ton of out of state plates here from all over the place. In the last month that I can remember, I've seen plates from California, Utah, Arizona, New Mexico, Colorado, Oklahoma, Arkansas, Louisiana, Alabama, Florida, North Carolina, Virginia, Missouri, Tennessee, Minnesota, Illinois, Ohio, Massachusetts, Connecticut, New York, New Jersey...?
As for the weather, I suspect people will adapt. I always think about what life was like for people who lived in the south well before air conditioning. I've been able to trace my roots back to Georgia to at least 1793. I always look at the Texas Capitol and an amazed that thing existed before air conditioning. I think what the street must have been like from drought to flood. I do much better in warm weather. I just hate cold weather and always have. I was already cringing last week when our morning lows were in the upper 40s, but our high today of 91F felt great.
And what I meant by "this fits" is just that California has a lot more people than say, Wyoming, which even though is closer to me, I pretty much never see any cars from there. I also see a lot of people here from Florida, and for some reason, I've been seeing more from New Jersey, which is a bit odd.
I love San Antonio and am totally biased about it on certain things - I was born there, but it has a different feel than the other Texas cities, and I'm not talking about the Mexican culture and old world charm its downtown has. I sort of think that wild growth that the other Texas cities have seen recently hasn't quite happened in San Antonio. That's not to say there isn't any, but there are places there that don't look like they've changed in 40 or 50 years.
Anyway, San Antonio has plenty of weather issues to worry with. They're 80 miles closer to the coast than Austin is and have had full on hurricanes falling apart over the city dumping rain down there. They're also farther west at the same time. Anyway, the Riverwalk is a gem and I don't care who doesn't know it.
There are plenty of good places to go there that aren't tourist orgies and that are legit San Antonio.