Do you go sometimes.......???

I agree that you should call first. I would be really mad if someone just showed up at my door unannounced and uninvited. I always call for that reason, and also I have to drive quite a distance to see my friends. If I called and said that I was coming and then they wouldn't let me in, I would be very angry and probably find some new friends. As far as feeling as if you are bothering them, have you tried inviting them over to your house instead? That way they don't have to play host/hostess and you won't feel like you are intruding or encroaching on their goodwill.