The above reply offers excellent advice. I'd add that you could even consider renting bikes, if you're close to where the TT will be. It's easier to get around on bike, and you can ride to your vantage point on the TT course long after the cars have stopped being allowed to drive through. So not only do you have less stress and more freedom of travel, but it's kind of thrilling to ride the same roads the riders will be taking in a few hours (it's also cool to set up early and see all the riders and teams recon the course, or even get passed by them). Of course, then you're limited with regards to what you can transport, but I found that even if you don't have panniers, you can take all you need for a tour stage in a good backpack/courier bag.
As far as location, you should think about what you want to see. Like L'Arriviste said, show up earlier if you want to view it from more than a random place, think of pictures, etc. But if that's not a big deal, you could go for an easier and comfortable option. I'm just thinking of the only TT I've seen, which is Annecy 2009. After going to Verbier, the start in Martigny, and the Colombiere, we'd seen some excitement at the Tour so we decided to set up on the downhill section of the course about 3km from the finish. In a little town there, we set up all day on the raised patio of a bar overlooking the road, so like 10 feet from the riders. So we got to see a good 200m strip of road, I timed every rider (which matched up with their finishing times pretty well), we leaned back with our feet up, had food and drinks at hand, and also had a TV in the bar if we wanted to check on the actual results of the stage or see how a rider was doing who was coming up to us. No crazy atmosphere of excitement, but it was a TT so it would be hard to get that unless you were at the top of the small climb or at the finish. I'm not sure what the layout of this year's TT is, and it sounds like it's the only stage you're going to see, so you might want to do it 'right' and get a spot by the finish line or something. But that Annecy experience was relaxed and enjoyable.