I was an absolute addict with D2 and never had a problem opening a town portal and going back to town until I was able to resume the game.
THIS... or just multi-task...
if i need to run to the bathroom
Answer: Pee cup.
or answer the door
Answer: Have megaphone ready and/or shout out the window with awkward sex noises. They will eventually leave... and/or call the ambulance.
Answer: Speaker phone? Bluetooth headset? or... just use your fancy caller ID, see who it is, determine how important they are vs. the importance of killing the mini-boss for the chance of a rare item... while you were debating and thinking, you have 1 missed call. Problem solved.