Rick,
Good on you for getting started. I had a track similar to this in Artin plastic years ago. It's one of the decent L shaped layouts. The thing to remember about L shaped layouts (when the long sides are against the walls) is that the driver stations have to be on the 6 ft end of the L....otherwise someone is always standing in the way of a driver seeing their car in a corner. I had 4 lanes and learned this the hard way racing against my boys.
Have you considered the "triangle" space and putting table across the ends of the L? It gives you more room to work and drivers across there can see the whole track. Might make marshalling more challenging but that depends on the layout........
Whatever you choose, the important thing is build it and race!