Clow Country doesn't really have seasons, being a desert. But Syaoran would like spring the most, once he starts traveling to other countries with Fujitaka (and later traveling worlds.) Sakura likes spring, too.
Fuumas have no preference.
Ran likes early spring because he likes watching rain. (lol emo kid.)
Himawari used to really like summer, but now she prefers fall because she doesn't have to justify always wearing a sweater in the fall.
Kurogane has no preference. He'd probably like whatever reasons his parents were born in. Hurrr he's a sap.