"How will the (cocaine) tourism and local & international communities be effected when people start dying because of overdosing or potential violent behaviour under the effect of these harmful drugs?"Why would they overdose if cocaine is legal?
Overdosing on illegal drugs is primarily caused by people taking too much of a drug due to a misjudgment of its purity or contents.
So that (for example) when someone thinks they're taking 1x of a particular illegal drug, they could actually be taking 2x of it (and that 2x is lethal, whereas 1x would have been just fine).
Alternatively, someone might think they're getting 1x of drug X, whereas they might really be getting 10x of drug Y or some unknown mix of drug X and Y, and the quantity of drug Y is lethal.
Such misjudgement, in turn, is caused by it being difficult or impossible to judge the purity or contents of drugs you buy on the street.
When drugs become legal they are labeled as to dosage and constituency, so their users will know exactly what they're getting, and overdoses will be minimized because non-suicidal users will simply choose to take non-lethal amounts.
Quality controls of the legal drug manufacturing process will further minimize adverse effects, compared to black market manufacturing which is a free-for-all in terms of quality (or lack thereof).
Users could, of course, still overdose if they mix cocaine with other drugs, but education campaigns should hopefully mitigate that risk, and in any case it won't be any worse than what happens when those same people mix effectively unknown illegal substances.
As for cocaine use causing violence, from my understanding it's alcohol that is most likely of all drugs to cause violent behavior, yet most people are not seriously calling for it to be made illegal because of that fact.
The violence associated with cocaine is mostly caused not by the drug itself but by organized crime syndicates warring with each other over control of the illegal cocaine market. This source of violence, of course, would be completely eliminated were cocaine to be legalized, as the market would be completely controlled by legal entities, and legal entities (like Pfizer and Merk) don't tend to war violently with one another over turf.