Yes they do pronounce it as Ho but it is a part of a slang called Hokkien. As for Hong Kong people they pronounce it as Hou.

Yes, they do. It is a accent. Actually, in different part of China, people's pronunciation is slightly different, because they speak other dialect, which influence their Mandarin. It is a bit like the difference between American and British. Hope it is helpful

People from Hong Kong seem to pronounce 好 as ho

Yes ,but ho is Taiwanese ,something like america slang

Yes, it is the Hokkien pronunciation of 好, variously also referred to as Taiwanese, Tai-gi, Hoklo, Fujianhua, Fukienese (older literature). Not a "slang" nor an "accent" but a regional language spoken through large parts of Fujian province, Taiwan and in South East Asian Chinese communities. Google "Hokkien" for more or "Minnanhua" for the larger language family it belongs to.