I don't think it's illegal as long as it's a public signal and not password protected, i.e. you didn't actually hack into their router, but, saying that it's still a kind of moral dilemma. It sounds like you're pushing this person's bandwidth and net usage up, which means they may have to pay more per month. That's kind of a shitty thing to do to someone, but, just to reassure you no one can search your net history unless they have server access, and even then they wouldn't be able to physically look through your browser history unless they were there in front of your computer.
Life is too boring with bare skin.