Is it ALWAYS rude to answer the call in front of someone?

[AmethystAnne]

OP, I think you were fine - you excused yourself to John and you were quick on the phone.

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I keep my cell phone on when DSon is deployed. One time I was in K-Mart, he called from Haiti (during the time when that conflict was going on).

[SisJackson]

I am one of those people that must answer a phone during certain times.  I am occasionally the on-call for a nearby facility and while it is rare for me to get a call, I absolutely must answer the phone if it rings.  I do try to warn my friends and family if it's my week, just in case they'd rather not go out for dinner (go to the game, have me over, etc.) when I might be interrupted.  So far nobody has declined and everyone is pretty understanding, even though the usual call results in me needing to leave wherever I am on very short notice.

I think as long as you keep the conversations short and make your face-to-face companions aware that they are as important to you as the phone call, that you're OK.

[Venus193]

In your exact situation, no. 

Sean had a crazy GF who took a call and was on for 20 minutes when I was there to cook and hang out with them.  It was obvious she was mediating a fight between her children (who were 7 and 9, I think).  She insisted she had to do this.  This was despite the fact that she and her children lived with her parents and both parents were at home at the time.

Unless there is fire, blood, or the police involved, this is a non-emergency and there should not have been a call.  Her parents should have handled it.

[JonGirl]

It all depends. I was in a store picking up an order when my phone rang. I left it.
The womans asks if I'm going to answer it. I said no, I was doing this first.
So unless the call is urgent or expected, I wouldn't answer it.