I've been to Amstersam twice now and I've always been stoned by just being in a coffeeshop, by the time I wait in line and get my weed I am usually already feeling a buzz!
Red Light District is what you should be worried about, I saw a lot of 'lads' edging each other on to go in and visit one of the ladies. On the second day I said '**** it' and experienced Red Light District to the fullest myself...