i'll assume when u say ur 17 and going to crete u mean Malia, the 'place to go' for drinking in Crete. I went to Crete when i was 17 with my mum and dad and stayed in Hersonissos a few miles down the coast from Malia, however most nites I and some friends went to Malia drinking. My mum and dad never went to Malia but a few years later they went through Malia and sed if they had known wot it was like they wud never have let me go at that age! However im a girl! i know that shudnt matter but i suppose boys can handle themselves a bit better. Iv since returned to Malia, its still the same, very VERY lively in late July/August, streets are packed and so are the bars, they dont close til 5am some of them! From a parents point of view its your typical drinking destination for a lads holiday, however, i have never heard of any trouble or seen any fights attacks etc when i was there, so in that way it is good and there are always police trying to drive through the copious amounts of ppl in the streets!
All in all its a great place to go, but please DONT hire the quad bikes/scooters they are so dangerous and 2 people died just outside our hotel on them the week before we went to Crete! anyways, hope u have fun!
Oh however, im not sure but some travel companies wont let a group of 17 year olds travel on their own, ie. atleast one of u must be over 18! we had this problem wehen we booked with Thomson Freestyle!