Study abroad in Hong Kong, should I start learning traditional?
simplified characters widespread enough


They're not. Most, if not all, road signs, newspapers are in traditional Chinese, and English.

Web sites are in traditional, simplified Chinese and English.

I would recommend learning traditional Chinese, not for surviving in HK. It's the culture, the literature of yore are recorded in this script. If you need to study further, you need to know it.

By the way, if you know it, you may compare the difference between Taiwan, Hong Kong, Macau and "that area".

Lastly, learning Cantonese and Mandarin together, well, good luck lah :)