I try to keep a basic ask for directions/ordering food command of several languages* and can still just about watch a film/sports broadcast in French (nobody really uses Latin or I might add that to the list) and would learn more but I find learning more science, history, electronics, computing..... far more engaging and I am all about the self pleasuring. However picking apart a language (written, spoken and in general) and seeing how it works (and how it came to be as such) is something I really like doing and it is no strange sight to see me reading up on this until the early hours, that said it comes in quite handy for a lot of ROM hacking and computing stuff (various clients have dealings all over the world and if I am the one that gets to punch their website/word processor into a form that can handle it so much the better). Part of learning history also calls for reading most of the religious texts so I am told I probably should get around to learning Arabic and related languages and probably Hebrew as well as translation there is an interesting game.
As for the matter at hand with most languages worth a damn being a mish mash of several prior languages and hundreds of years of history they are all largely illogical, counter intuitive in general and counter intuitive between each other (applying grammar of one language to another fails more often than it works in my experience) messes that would not be tolerated in almost any other intellectually driven field save for when it is a law of physics being the unintuitive one. Similarly language is a skill most are encouraged to pick up early on and is fairly deeply ingrained (several have already mentioned the difficulty in listening and different sounds between languages is a fairly well considered part of the study of different languages). To that end if someone feels like overcoming the ingrained thing and doing the borderline memory test that playing in other languages entails (let alone in real time) I can see no good reason to do anything negative.
*I do not usually find this so bad to learn and deal with, trouble comes when people want to pepper directions with slang, mumbling or a nice amount of adjectives... trouble is I also find myself doing the same when asked unless I force myself not to.
Re: accent at a party- the position of token foreigner is an esteemed one at any party. Should you find yourself in a party where that is not the case my advice would be to leave as you are wasting your time there. Bonus points if you end up with the situation reversed with yourself in the middle of it one day, granted that usually falls hand in hand with your token foreigner friend seeing if anybody wants to ride shotgun in a flying visit to wherever they came from and those are equally amusing even if you do not end up at an impromptu party.
I mentioned it in the last few similar topics but I do feel the need to share my two favourite experiences here- one was walking through Liverpool in 2005 or so and a couple of ladies were speaking in Arabic before switching to pitch perfect scouse (truly pitch perfect- if I said piss take most people jump to the hamming it up style but that would not be what I meant if I said piss take here). The other was a couple of years later when I was in Amsterdam in an Irish bar- the barmaid there had apparently been there for years and developed what can only be described as a completely neutral but heavily pronounced* Irish accent.
*head into the sticks in NI or ROI and you still know you are there but only just if you expect Belfast, Dublin, Cork, Galway or Omagh to be the only accents available.
Re potatoes. If the little flag in the bottom left of your posts reads USA consider that it is as galling to walk into a supermarket when stateside and see potatoes called just that* as it would be for others to assume
soda/pop/fizzy drinks/soft drinks come in just cola and lemonade forms (if you have not met that yet a warning that you will should you venture into much of Eastern Europe and especially outside the bigger cities there).
My favourites-
http://www.shrubs.co.uk/ekmps/shops/shrubscouk/images/potato-second-early-anya-2-kg-14981-p.jpg
*there is such a thing as a potato aisle in most supermarkets that aspire to be more than a corner shop.