It conveys: stop lookin at my meal - you're not getting any!
With regard to con permiso, common everywhere in the spanish speaking world - the response in most places is, "si, pase" or something along those lines, in the DR the common response is "si, puede", or just "puede" - it's a formality, nobody is really asking for permission, but the response is that its granted.
Another response that I find interesting. When asked "como estas?" or "como te sientes?" (how do you feel?) a good chunk of people won't say the usual "bien", but rather "normal" - which I guess is an honest answer. "Como te sientes" would definately be a regional thing - I've never encountered anyone of another nationality that I don't know ask me this.