res conn execute t_users join t_cities_in_users t_cities_in_users user

   res = conn.execute(t_users.join(t_cities_in_users,
            t_cities_in_users.c.user == t_users.c.id)\
        .select()\
        .where(sql.and_(
            t_cities_in_users.c.city.in_(cities),
            t_cities_in_users.c.question_notify == 1)) 
    )