Oh ahahah =} you do have magical powers!
Oh, I found your comment was deleted again =/
This time though is not quite like the other that I will respond to more in a bit.
I wrote the comment here, and then in a flash, just as I hit, "post" understanding came about what you were saying... so I immediately hit "delete" then thought, 'oh, he's going to get some sort of notice for that...' =]
And here is it again! :D
Anyway, I was thinking boundaries as in edge (or one side, like of a square), but on looking it up on the google it also comes up as border (margin) so I was not so far off.
Yes, you were right in your guessing (in/on/at... I never know =P)
Magical powers?? hahaha... of course not. I usually delete unnecessary things, questions people ask 200 times, swear words, etc. Some posts have more than 30 deleted comments, or else, it would be really hard to read useful information...
I cannot think of any context right now in which «a banda» would mean "side." It should not always be accepted regardless. Think of the word "side" or "bank;" these two words in their conventional sense would be translated as «lado» and «banco», but there might be a suggestion «ribeira» for either one of these words. The problem with this is that «ribeira» only means "side"/"bank" as in "riverside"/"riverbank." This suggestion of "side" might be one of these cases in which it can only be translated as "side" in a very obscure circumstance/context and should not be translated as such in most cases.
In another comment from 3 years ago, the mod here provides an example in this exercise discussion, "o que te traz por essas bandas" so in that way "side" I believe means, this side/the side, the other side, far side, a side, one side of... town, the state, the country (and so on including probably campus & building and the like), synonymous with part which in itself has several different meanings not covered by side (though they work together for a side-part but that's an english tangent).
Yes, a "band" of people, if you will. :) However, if you will notice, it is not frequently used, according to priberam: http://www.priberam.pt/dlpo/banda. The masculine «o bando» is used more often: http://www.priberam.pt/dlpo/bando. «multidão» is a better word for "crowd" and «gangue» for "gang."