My opinion changes based on circumstances. Hard drugs are an adults choice, if there are no children around, as far as I am concerned. If adults are going to do it and stay clear of children while they do it, it's their choice. If adults are going to do it and be around children, they need a good bonk on the head before being sent on their way away from kids.
Softer drugs, like weed... under the influence around kids, not really a problem, but I would prefer adults and teenagers wait until the younger ones are asleep and in bed for the night before engaging in such activity. Although if you do a lot of it, since it is a slight hallucinogen you probably shouldn't do it with kids in the home (yes, I have had some medical grade stuff, and enough of it to screw with my mind, so I know it can fuck with you in a serious way).
The legality of all this stuff, I think people should take a lesson from Amsterdam... legalize it and be done with it, reasoning? Because, once it's legal a lot of people will loose interest in it because it no longer holds that "rebellious" statement. If it's available everywhere, all the time, the sneaking around and doing something deemed 'wrong' and the rush some people get from doing that will disappear. Yes, there will still be hardcore druggies and issues with it, but I think it will lesson the fun in it enough that drug rates and usage will go down. Again, keeping yourself away from children while under the influence would be a must in my book...and with the harder stuff, keeping yourself away from kids for 24-48 hours from the moment you start doing it would be required as things like meth/speed and coke can seep out of your body and can be transferred through touch in minimal amounts (and even a minimum amount could effect a child in a bad way).
Anyway... in my own town? Well, the closest one to me, there is like a one stop shopping center for just about anything, and if they ain't got it they can either point you in the right direction or have it within a few hours. But I also think they should have someone clamp down on them as they are dealing the hard stuff to teenagers and kids, which in my mind is wrong (especially when they are trading this stuff for sexual favors to kids). And having had, recently, a very bad experience with acid and coke, I can safely say its not something even a teenager (16-17) should have access to, let alone anyone younger...I barely held on to my sanity, a teenager/child would not do well with access to either of those, specially when the two are combined.