I've been confused with those geeks way too many times (not just by japanese, even waps themselves. Though, it's better to have them yell at me that i can't speak japanese than for them to sit and pester me about their イヌヤジャ or their ナルト). I've taken offence to it quite a bit.
Usually once people have a certain idea about something (especially other people) they are a pain to change the opinion of. Heck, i might even ask a question i want answered, that dosn't seperate me from the wapanese.
Um, what exactly is your situation back home? Are you at Uni? Are you taking classes in high school? Are you in adult classes? What situation are you in where you are constantly being confused in an awful way for geeks? Is it hurting your learning because people aren't talking to you? Is it getting in the way of trying to pick up Japanese girls? What exactly is the problem?
If your eventual goal is to come to Japan, then you likely will have no problems like what you are describing. Adults in Japan are busy, normal people and will not treat you any extra differently because of associations with 'anime freaks'. They might not even know that Japan can be considered highly geeky by people outside of japan--one of my friends here was shocked when I used a phrase like おたくの楽園 to describe how many overseas view Japan.
As everyone here is trying to say, speaking a local dialect will only hold you back. You will spend time studying less useful things, you will look very insincere if someone asks you how/why you speak with an accent (assuming it were even possible), and the most likely outcome will be that your Japanese will seem strange, not accented, and so people will be more likely to switch to English or assume you picked up your Japanese from anime. In all, very counterproductive. You also have a lot of the more knowledgeable and helpful posters on the website all trying to give you advice--its advice you don't want to hear, but taking advice you don't want to hear is one of the best/only ways to improve. If you don't learn how to take advice criticism, getting to a high level will be quite a struggle.
Are you a native? I was always told (and noticed on my own) that natives typically don't say such things like that. And only a native would be able to determine my ability, so, by rating me as a non-native, you are becoming a hypocrite for trying to be something you're not, which is what you're accusing me of doing.
Do you really believe this? Certainly the final judge on difficult issues such as translation should always be a native, but its certainly possible for non natives to determine ability. You probably do it all the time yourself by judging the other people in your classes. I certainly do it with every single non native speaker I spend any time with, because it helps you know how much you can use and be understood, or to what degree advice from the personal would help your own studies.
I went out drinking with a couple Japanese and a quite good American the other day and was quite happy to have the American correct me on a few occasions (he did it in quite a subtle way). He was someone I could learn from and I did. Choosing not to learn from people who can teach you is, again, a counterproductive way to study. And, if your eventual goal is to come to Japan, you will probably spend time in mixed japanese/foreigner conversation. Maybe even with 'anime geeks.'