热烈祝贺第八届花博会胜利召开

Heartist congratulations on the opening of the Eighth Floral (Expo)Exposition . We will you great success.

中式标语，中国味很浓,怪不得大家都觉得很难翻译
Congratulations on the successful opening of The Eighth Flower Exposition

A w热烈祝贺第八届花博会胜利召开
Warmest (heartist) congratulations to the Opening of the 8th Floral Exposition (Expo)