SELECT rider_names FROM table_27833186_1 WHERE location = "Euer Valley, CA" AND horse_name = "Magic Sirocco"
Siapakah pengendara kemenangan Kejuaraan di Euer Valley, CA dan kudanya Sirocco Sirocco siapa?
CREATE TABLE table_27833186_1 (rider_names VARCHAR, location VARCHAR, horse_name VARCHAR)