In response to that...
Good job on the Pre-N router purchase. You definitely won't regret it. As for Mac compatability, I honestly know nothing about Macs to accurately comment on that subject.
Hopefully someone will join in here, but I know you couldn't network the two computers from the one with the card (as a host) via an ethernet cable, as they are different OS's.
You did however mention, "...so now I need a wireless card for my new PC Desktop."
If you are setting up a desktop in the hotel room, you would need a CF>PCMCIA adapter to use the card I posted in the link (and that's assuming you have a desktop with a CF slot, which most do not), or you would need to purchase the desktop version w/ card adapter:
http://www.ebuyer.com/customer/produ...156886&_LOC=US
You also asked, "In general do the PCI cards perform better than the USB cards?"
I have never heard of a USB type of 802.11n connection.
And as for the "cantenna"...it seems like a hoax to me. I know about radio frequency tracking from high altitudes, and typically with more gain there is also more interference involved also. This could mean more info lost/corrupted than gained, reason why you don't see huge extending 3-G network card antennas. It's the source which transmits the radio frequency (wireless router) which would need to be improved upon, which is also regulated by frequency output power laws, unless it's approved as a commercial device.
What you truely need my friend is a repeater (or referred to as a range extender) which simply plugs into an a/c outlet...find a pop machine halfway between you and the source and hide it behind there well, he he.
No, but what I would really do is find out your details asap (room location in relavance to the network source, network type, how many routers, etc). They should be able to find you the details if you ask.
Your room location might just put you out of luck, sorry to say.