Well I did something similar about 2 weeks ago.
I have a sitting area off of my master bedroom were my PC's are at & were my DSL is. Now I needed to get down to my first floor as well, & fortunately the wall where the entertainment center is, is where the air intake is for my A/C on the first floor. So I went up into my attic from my sitting area & then across to the large intake hose ehivh about 18 inches in diameter & cut a small hole. I then dropped 2 runs of RG6 & one CAT6 all the way down to my first floor. Then I took off the cover on the intake downstairs & made another small hole & put the wall plate directly below. It looks like it came with the house, because luckily for me, the low voltage wall plate is perfectly lined up with the normal 120 outlet about a foot away.
Now I suspect that you would probably have to do some runs once you got down to the first floor, but at least this way, all the cables are inside your house.