I've never heard anything about mids not wearing uniforms on campus. Although, I'm sure they get plenty of dirty looks, considering the very anti-war atmosphere. I'll find out for sure when I go up for orientation.
There is a lot to like about Cornell. Everyone I talked to who went there had positive opinions of it. What turned me away were its weather, its cost, and its location. I'm from sunny SoCal, so Cornell is about as far away and as different a climate as it gets.
Lastly, regarding the scholarship activation... I don't know about Penn, but there shouldn't be a problem having the navy pay tuition at GWU. The GWU nrotc site highlights the scholarship program quite a bit, so it's hard to imagine that the navy wouldn't pay for GWU's midshipmen ...just my observation.