so I'm guessing this one is more suitable at a bar rather than said to a waiter before ordering?
Not really. Будьте добры is okay everywhere, no matter if you are at a bar, or telling that to a waiter or to your friends at dinner.

an old man saying "would you be kind and get me a beer"
At a bar? In a pub? I thought that would've been "be kind and give me a beer". I can imagine get to sound normal only if the old man catches someone outside a pub and ask them "son, would you be kind and get me a beer...". Though I sure may be wrong on that, my sense of language may be playing up. Correct me, please.

so I guess I could see my self saying дайте мне нож пожалуйста but maybe saying можно мне or я хочу for a блюдо.
Maybe that's a difference between our waiters but here in Russia when you come to a pub or a restaurant you take your sits and take a menu usually lying on the tables or on the bar. Then, a few minutes later (to let you pick items you want from menu) a waiter shows up and you tell him what you want. He disappears and then brings your food, drinks and dinnerware (except for those that were on the tables initially when you landed on the chairs). So it's quite normal if you tell either of "я хочу", "можно (мне)", "дайте мне", "принесите мне"... to a waiter (of course, you can use some of the "пожалуйста", "будьте добры", "если (вас) не затруднит" to sound polite). That refers to both dishes and dinnerware.

And is there any difference between saying simply можно and adding мне? or is the мне just usually implied so therefore can be omitted.
If you are alone you can add "мне"; If you are in a company of your friends, you can add "нам" but usually it's implied and there's no need to explicitly point the receiver out. Of course you can say "можно (принести) два бокала вина тем очаровательным девушкам за крайним столиком?". But if you didn't specify "кому", then "мне" или "нам" are implied by default.