As I recall, the 'usual' LM traffic, which is never going to be great but certainly not as bad as leaving Après-race, from one of the car parks!
We went South down the D147, running parallel to the river, until getting onto the D338 which took us round LM and up to towards Saint Saturnin & onto the A28. A bit sticky, until you got onto the D338, then slightly less so all the way to the motorway.
I suppose you could schlep up into LM, crossing the river & going North, but we found the road was ok & used it. Think it's one of those 'play it by ear' things, though.