This has not been my experience. I find most cabs have decent A/C. And the Dial 7s and Carmels of the world don't offer newish town cars. If the OP wants to pay for a premium car service (like Elite -- 800-472-1123 -- which we've discussed in other threads; they charge about $75 all in), then he'd be assured of a later model car and good A/C. But, as I've said, I've had good luck with A/C in NYC cabs.