How can I get from Guangzhou Liwan District (Holiday Inn Shifu) to Sunflower Gardens?

You can take subway line 1 from Changshou Road to Yanji Station. Then transfer to line 5 to Chebei South Station and line 4 to Jiaomen Station, Exit A. The duration is 90 mins. And the ticket fare is CNY 11 per person. Afterwards, take a taxi to the destination directly. The cab fare is about CNY 90 in usual time.

Hi, may I ask if taking a cab/taxi from Holiday Inn Shifu directly to the garden will be easier? I have 5 person travelling. Roughly how much will it cost to take a cab?

Yes, it's ok for you to take a cab from your hotel to the destination. However, generally speaking, one cab can only accept 4 passengers at a time. Thus you need to take two. For one cab, it would cost CNY 270-280 for the single trip.