Well, I can honestly say that it has affected my holiday, but not really in a big way... just the minor of annoyance of many of the hotels being fully booked in "low season". I had days to play around with, had I known, I'd have moved my time here a little. But only really for the hotels. Where I am staying, I havent seen any sailors, but the price is pretty high.
Otherwise, I've seen plenty of them out & about, some very drunk, but most were somewhat sober. They were typical young men... a little too loud, a little too attention-seeking. But hey, we were all young men once, and likely acted the same. What I've seen is that its a mix just like you'd get with almost anyone... some very decent, well-mannered types... some in the middle that are OK, but get a little mouthier as they get more maow... and then a few that embarrass themselves. But the buddy system often works well in those situations. You rarely see the guys alone... mostly in groups of 2-4. And they tend to make sure any drunken troublemakers (even ones not from their group) are kept in line. Going out into town is a privilege for these guys, not a right. If someone screws that up badly by getting into a fight with cops, or causing any kind of public spectacle, and ALL the guys could lose the right to go off ship. So, out of self-interest, they very much self-police. As such, there's rarely trouble with them.