>>Nobody in San Diego leases vehicles with climate controlled cargo areas for long trips (one way). They'll only lease them for local use. Unless you know something I don't.
I've done it from Utah to TN in the middle of summer, but that was 20 years ago. I don't know if anyone rents them any more, but at the time I was able to get a rental panel truck with a pass-through door so that the air conditioning got from the cab to the back. I transported lots of dogs, cats, birds, fish, and a few snakes with no trouble. I only lost a coupla fish who jumped out!
Driving at night would definitely help. If you can find a portable A/C, that would be great. Orrrrr....how about renting an extended Econoline van one way? Would that have enough room for all the snakes, if they were transported in bags or small boxes? Hmmm.
As for babysitting -- do you have to close out the place you're leaving before you leave? If you can leave the snakes there temporarily, it should be easy in a big place like San Diego to hire a college kid to watch the snakes for you. That's another alternative -- take them in batches, maybe....
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0.1 Peruvian rainbow boa (Amaru)
2.0 Brazilian rainbow boas (Arco, Olho)
1.3.1 Honduran milksnakes (Chicchan, Chanir, Hari, TBA)
1.0 Thayeri kingsnake (Coatl)
0.0.1 Mexican black kingsnake (Mora)
2.7 corns (Cetto, Tolosa, Uce, TBA)
1,000,000.1,000,000 other critters