Can Guangzhou people understand Huaiji dialect?

Of course. The characters in Huaiji Shangxia belong to Guangfu dialect, one of the three major dialects in Guangdong. Guangfu dialect includes Guangdong dialect, Guangzhou dialect, Hong Kong and Macao Cantonese, Nanfanshun dialect, Xiangshan dialect, Wuzhou dialect, Guan Bao dialect, Dongguan dialect, Baoan dialect, Luoguang Cantonese, Siyi Cantonese, Laiwen Cantonese, Yongxun Cantonese, Goulou Cantonese, Qinlian Cantonese, Wuhua Cantonese and Ying Cantonese respectively.