I went to Le Mans a few years ago, when Dovi took out Toseland on the first lap, and really enjoyed it having been a lifelong ambition. I got to the train station in Paris too late on the Saturday, so I had to change my plans. First TGV out of Paris was at 8AM on the Sunday and it took an hour to reach Le Mans, no stops. Once you get to the train station, right across the road is a tram station which had recently been extended. The tram dropped you off very near the the back straight/garage vert corner and you could pay at the turnstile at the same price as pre-booked tickets. My problem was that I had to collect my ticket so I had a long walk, but walked on the first bit of public road of the 24hour course. If you have to collect tickets, I got mine at the exhibition centre which is roughly level with the Dunlop bridge. There are a few underpasses, one near Dunlop bridge and another underneath the back straight if you want to get in the middle of the two bends before Garage Vert, but it took a while to get out as the tunnels weren't that wide, I had a sit down and let it clear.
There was a ramshackle campsite behind the back straight, I believe it is free to camp on designated sites in France. There were loads of English people there, every other bike/car I saw had a UK licence plate. There was also a free programme although there were loads of adverts in there, but no translations. Never seen so many 'Busas in one place, looks like the French love em.
Word of warning for anybody wanting to train it all the way, Gare du Nord (Eurostar station) and the Paris station connecting to Le Mans are miles apart. Travelling on the subway between the two stations took over an hour, that's why I missed my Saturday connection.
I plan to return there one day