Tidus's is heard multiple times throughout the game.
Yuna's is the Besaid's beach theme (beach only, not the village), also heard during several of her lines.
Wakka's is not heard through normal progress (or too short to notice in full). If so, then it quickly switches between his and another song. Possibly during certain events in Luca, but one should remain skeptical.
Lulu's is heard during the conversation with her former summoner (the dead one, not Zuke), as well as the duel with Yojimbo (also in CoSF).
Auron's is heard several times during the game, particularly when he leaves at the end.
Rikku's theme is also heard during some of her lines.
Kimahri does not have one. The closest is "Guardians of the Mountain"/"People of the North Pole".
Seymour, no, really?
Jecht's is heard in full during 8 of the 10 Jecht's Spheres.

This IS an accurate location of the themes.

I like Yuna's the best, especially an arrangement of it, Movement in Green, and The Fleeting Dream (area of Zanarkand).