Having worked in a hospital I can tell you it all depends on why you are in the hospital. If for any reason you are in the hospital for a remotely life threatening condition or post major surgery, a catheter is a must to monitor kidney output to avoid renal failure from secondary complications (or direct if you are in the hospital for renal issues). This is VERY important information. Diapers are a last resort always as it makes it difficult to measure output. If you do not have genuine incontinence, aren't in any serious risk of renal failure (internal bleeding, clotting, and more), and able to measure your own output in a "hat" (urine measuring device that goes over the toilet bowl) you may ask to not be cathed if told one is necessary. To cut you off at the pass now, weighing diapers does not work particularly for adults because there are not published standards for adult diaper weights as in pediatrics. Look, I enjoy a good medical/diaper scenario as much as the next person but, unless you truly are incontinent and cannot manage to "sack up" and deal with a cath and most importantly, truly unable to help yourself...then yes go for it ask for a "brief". Truth told, in that particular scenario (only) the nurse will probably appreciate it verses helping you with a wet bed. The moral here is, Caths are for a legit medical reason when used in the hospital, not just for convenience, everyone hates them but, if they say you need it there is likely a good reason.
I hate caths. They wanted me to straight cath but, that was unacceptable to me I'd rather be diapered for day to day incontinence. If I am in the hospital though and they want me to have a foley I am going to do it. You have the right to ask why...likely they will explain as I just have. If that is the case don't be dumb and don't take chances with your life. Don't be a creep... be smart.
If you desire that much to wear diapers in the hospital for kicks...go for it but, bring your own, take care of yourself, and be polite about it. I guarantee no one will say anything to your face about it...lol.
Disclaimer: Those who know my posts know I am not one of those over conservative don't ever wear diapers outside the house, don't ask help when you need it, don't push the bounds kinda person. Again, it is that this topic deals with a serious medical/ life sustaining topic. To encourage anyone to do anything against medical advice especially, when already in the hospital is irresponsible and ignorant.
*steps down from soapbox*