I go by myself all the time. I've only gone with other people maybe, two or three times. Every time I've gone with others, the people just are a-holes. Running around scaring the bugs and fish myself or others are trying to catch. The last time I went, this girl and I were being friendly to one another and wanted to do a tour together but this other guy was being a dick and wouldn't let us and then he error'd. I was so sad. :c So, I just always go by myself.
I go by myself at night for beetles. The only reason I usually go on public tours is for stuff like giving out free bells or just having nothing to do so I just go and talk with random people and go on tours and act friendly when I'm usually like graaaaar
Others for a social experience. It amuses me talking to people from Japan that can't understand most of what I say. :3 people also tend to compliment my custom designs so that's good too.
I usually go with my friends and fish/play games with them.
I don't go often by myself just because I find it boring.
I have plenty of ingame bells so I don't really grind for them anymore.
I only go with others to island hop for items in the shop. I've met some good people and played some tours with people, but I've also run into a lot of weirdos.
I almost always go with others, because there's many possibilities, kind of like a box of chocolates, and I find playing with others more fun. Club Tortimer is the reason why I kept playing ACNL in the first place.