Hi Nigel,
The short answer is no. I haven't towed along the west coast of Lake Garda, at least no further North than San Felice del Benarco.
The longer one is, no I wouldn't because it was interesting enough solo and because the easter road is better for caravans. Don't get me wrong, it is not one of those "you couldn't fit a caravan along there" of roads; it is just (between Gargnano and Riva Del Garda) bendy, riddled with tunnels that have bends (and junctions in them) and often has something big, such as the local bus, coming down the middle of the road at you. But, it is indeed a bus route so there is actually no technical problem in fitting a car and caravan on it. I would use it if I had to.
The Eastern side has a much better road for making progress, inless you are there in the height of season when there can be quite a few holdups for sheer volume of traffic.
If you are in the area, it is a very pleasant drive solo, with some stunning views of the lake.
Cheers
Mike A