Baiyun airport is far from downtown （about 40 KM）. Shangxiujiu is a shopping street in Haizhu District.
You can take Guangzhou airport Express to downtown Guangzhou. Then take Metro.
You can refund the unused value, but only in Guangzhou Metro's specified office (not easy to find).
Any help need, pls ask in Guangzhou4u.com

Hi, Mrs.ELIN
when you arrive at the airport, you can take the airport express Line 1, and it'll take you about 45 minutes to go to the booking office of CAAC which is near the railway station.Then transfer to BUS31 at railway station, get off at DA XIN LU KOU stop which near Shangxiajiu.
For the transport store value card, which is called Yang Chen Tong in Guang zhou. There're monthly bus value card(only for bus)and monthly metro value card(only for metro) which you can buy at the metro station or at 7-Eleven. monthly bus value card cost RMB88yuan for 90times（applicable for most of the bus）, monthly metro value card cost RMB55yuan FOR 20 times or RMB88yuan for 35time(applicable for Line1 to Line 4).
But I suggest taxi is the more convenient vehicle and it's cheap in Guang zhou.
Enjoy yourself in Guangzhou