First, I wish you the best of luck with your gastric sleeve procedure. This is a big choice and I hope that you are able to attain your desired weight loss goals! This decision is definitely a personal one for you. In terms of safety, there is no problem having fillers done before surgery. Although the weight loss will hopefully be dramatic, it usually takes several months before "big" results are noted. Therefore, the filler will already have some time to have been in effect and to start dissolving away. As fat is lost in the body, it may be lost in the face as well (not necessarily at the same rate as fat in other places). Therefore, with less facial fat, the nasolabial folds may become less prominent, making the filler unnecessary. There is always the chance that you will want the filler taken out if it does not look right after the weight loss, but that is up to you. Alternatively, you could save the money for now, and put it towards a celebratory rejuvenation fund for when you obtain those awesome weight loss goals. It depends on your priorities! Good luck!