I try not to, drummer.  I have though, but because I needed to.  There have been some cold days up here and at the time, I only had USF sweaters/jackets.  But believe me; everyone at my program knows I'm a Bull first (just from conversation, etc.).  I have a USF license plate and I have a USF Alumni sticker on my car (I also have a Duke sticker).  I also think it's different for grad students and people that have a direct affiliation to another university (like in your case).  I also don't have problems with faculty and staff members that wear them, since it would be fine at any other job (and for those people, working at USF, etc. is there job).  You could "tell" that they are not students and they have to be on campus to work or something.
The problem that I have is this.  The students that attend USF and come out in FSU, UF, and UM colors and belittle USF.  I have seen it happen before.  "USF sucks my balls... go GATORS!" is one example.
I can add a million other cases (OK, maybe 20 more).
I would never belittle the school that you I am currently attending.  I had a former roommate that did and I gave him hell for it.  He finally transferred to UF to be closer to other friends... but in his case, he was a UM fan.
I just think it's simple to just avoid wearing other colors on campus.  If you are a USF student (say an undergrad) and you are randomly wearing a UF shirt on campus.... then I HAVE a problem.
And like I mentioned... I wouldn't wear a Duke shirt on USF's campus when I am visiting (say in the middle of the summer).  That would be random and not necessary.
I try my best though... if Duke won a national title and I was planning on being at the USF campus the day after (and I was planning on wearing a Duke shirt that day), I would make sure that I had an extra shirt to wear before stepping on campus. ÂÂ