I really wouldnt bother going in the summer. I have done many a summer race training on glaciers, and I can not see why anyone would want to do it recreationally.
Its cold first thing, but by the time you finish you are sweating buckets, and your boots are wet. The snow goes from hard to slush, and is only decent for about 30 minutes.
Then there is the time it takes to get up and down the mountain, the ques.
The fact that a large area will be taken by national squads training etc.
Its worth going for a novelty morning or 2, but not basing your whole holiday around it.
Go now though, there is bucket loads of snow currently