First off, I'll say that wherever you are heading or whatever you are doing padded in public, no one is going to have their eyes trained on your rear and even if they do, they likely won't even stop to question it. One of the important things to do when wearing out and about is to simply keep your head held high, remember, chances are no one is going to notice and even if they do, they certainly won't bring anything up
In answer to your basic question, how noticeable a diaper is depends entirely on the brand. Store bought brands and medical brands tend to be a little easier to conceal as they aren't nearly as thick as AB specialty diapers and they don't have those cartoony and cute all-over prints.
That being said you can easily wear AB diapers out and about, if you intend to do so though, form fitting clothes are not the best route to go, especially if you're anxious about being caught. Form fitting clothing will accentuate the bulge and the diaper's shape. If you want some advice on how to minimize the chances of your diaper showing, one of the things you can do is avoid using a stuffer, if you use any at all and to avoid fluffing the diaper before putting it on. Also, during the handful of occasions I have worn out, I usually put a pair of underwear over the diaper as it effectively collapses the diaper a bit, restricts the bulk and muffles the crinkles. I also wear a baggy pair of track pants or khakis when out and about, pants that aren't very form fitting and that can easily fit over the diaper and underpants. Every time I have done this, I have yet to be found out, no one was the wiser. Another small thing that helps, is tucking in your shirt, this really prevents that telltale waistband from poking out at the rear and if there's one thing that is bound to be a giveaway, it is a waistband complete with some very babyish designs.
For you, since I doubt you have a pair of male underwear lying around, baggy clothing will be your best friend. As I said, wearing form fitting clothes will only make the diaper standout more, this is something that will likely make you feel more anxious about wearing out. If you have pants that are a fair deal larger or baggier, just throw those overtop your diaper, that should do a more than sufficient job of concealing it. Of course, the only thing I'd be worried about with Crinklz is the sound. When dry, Crinklz aren't nearly as thick as the ABU brands I usually wear out and about, but Crinklz are rather noisy, they certainly live up to their name, they are a very crinkly diaper from what I can remember. Without the use of layering i.e. putting something over top of the diaper before putting on your pants, you might have a hard time concealing the crinkles. On that front, I guess you could practice walking with a diaper on under your pants to see if you can walk in a certain way, so as to minimize the sounds.
I hope this helps and once again, remember, when you are wearing out and about, no one is even going to notice. Most people are too busy worrying about what they are doing and where they are going, their minds are elsewhere and most certainly not on your choice of underwear
Good luck