I am a member of Talwalkars. They are pretty good if you arent looking for someone to be with you ALL the time. When you have a new workout, they will teach you properly and after that you are on your own, more or less. I personally dont find this a bad thing.
I also havent really asked for more help but some people do and they do give them quite a lot of personal attention. If you plan to go during the morning between 6 and 9 and in the evening between 6 and 8:30, forget about finishing your workout in a hurry. The gym is so crowded, it is difficult to walk without bumping into someone.
I am talking about my experience at the Jayanagar branch. The new JP nagar one is supposed to be bigger.