I have belonged to Migros Fitnesspark on and off since I arrived in Zurich. I recently rejoined and normally go to their facility at Puls 5 which is pretty modern and luckily... for some odd reasons... never too full at any given time of the day. Staff is always very helpful and friendly and many of them do speak fluent English. Plus as all the Fitnesspark gyms do, they have all the bells and whistles to help you relax after a "rough" workout. They also offer a large array of aerobic classes. The only downside is that you always have to pay for a full year membership in advance but on the bright side, they do accept credit cards.

As far as insurance paying for a part of your healthclub membership that is normally only possible if you have the supplemental insurance. Basic insurance does not cover healthclub membership. There again, on the bright side, and in my case, my supplemental insurance costs me 600 francs a year and my insurance pays me 90% or 600 francs of the healthcare cost. Since my memberships costs 1100 francs a year ( I know... robbery considering I used to pay for similar facilities 50 dollars a year for my gym membership in San Francisco with 24hr Fitness - one of the advantages of having been a member with them for almost 10 years) the supplemental insurance is basically paying for itself.

Anyway, if you are only looking for a place with nothing more then machines to work out, there are two or three new gyms in town whose membership rates start at 29 francs per month. Just google them.