I think you should definitely take the deal with the trainer, specially if he has good references... THAT is a great price. I also think starting at going only twice/week is better than not doing any weight training at all. Weight training will build muscles and in turn muscles burn calories more at rest, and we all like that idea don't we
... Also, look at your schedule carefully, there must be ONE other time during the week that you could go to the gym, I definitely think you should make the time for weights. Just make sure the guy has good references...