I've only done K once & that was back in 2004 so take what I say with a pitch of salt as I may be misremembering some of this...
But when I was "high" on K, I seemed to recall everything felt floaty...a bit like the lack of gravity in space. So IIRC I didn't care if I jumped off bridge as I thought I would fly / float down safetly or was too high to care. Can anyone relate to this?
Whilst that is the positive side, the negative side was I probably couldn't co-ordnate myself to get to the ledge whilst high off K.
So to sum it up & from my vague recollection of K. If you are sat in the place you are going to jump from, then I would recommend it. If however you need to travel to the place of jumping & do some work to get ready (i.e. take trains / climb over fences / avoid patrols / security etc), Then i'd imagine K wouldn't be good for that.