I had to search around a bit until i found this club in cologny. http://www.cs-cologny.ch/index.php
It's not cheap, but it is really nice. Non-member can hire a court, but it's pretty pricey at 32 CHF a pop. However, if you become a member then you can play as much as you like with no additional charge.
It's not exclusively ex-pat, as there are many many french speakers there, but everyone i have met has been very friendly and they have a club, kind of turn up and play and meet people night on a weds (although not running throughout the summer).
There is another club up near the airport which was just a bit too tough for me to get too. See here http://www.geneva-squash.com/index.php
but looks friendly too.