I go to my own country. I'm naturally awkward in social situations, so I'm not sure how to say, "Sorry, I don't speak [language]" without it being taken the wrong way at times. However, a lot of the UK island is pretty bland, so I've considered risking it.
When I am extremely bored, I go on.
I prefer international. NA has way too many people who try to hustle me for bells... aka 8 year olds lol
correction - they want to hustle anyone. :|
I usually choose to visit my country's island, and I visit at strategic times of the day to minimise the chances of running into other players.
I only use Club Tortimer to look for exclusive items in the gift shop, and I feel so rude when I leave almost as soon as I arrive.
(Also I'm pretty shy so I don't much like socialising on Animal Crossing anyway!)
I prefer the international island cause I usually meet really nice players there whereas on the regional island I tend to run into the same kids I've met before who just try to hustle people for their bells.
Usually international, because without fail, if I'm going to just my country (North America) I run into scammers or rude people who flick the wifi switch for no reason.
I really really wish there was an option to turn on a Japanese keyboard, though. I run into Japanese people a lot and feel weird because I can speak it, but it's really hard to communicate without Kana. That's really my only problem with the international island.
I use the NA feature because I'm one of those people who get really anxious in CT when someone new comes in and I don't know the same language as them.
When I'm island hopping for items I'll alternate between the two so I'm less likely to run into the same people. Other than that it depends. If I actually want to talk to people I'll typically go to NA, and if I don't, I'll go international, so if I run into someone who doesn't speak English it's a good excuse to not have to talk, ha.