I had a lap rny also. My surgeon inserts tubing during the surgery for a device called an on-q pump, which provides a time released local anesthetic (similar to lidocaine) directly to the surgical site. The on-q pump works for about 5-7 days after surgery. I was also placed on a morphine pain pump for the first 2 days. I it helped a lot the first day, by the second day I didn't need it as much and switched to asking for lortab (liquid vicodin) as needed. By the third day the pain had lessened even still. When I was released on the third day, the pain comprable to say, having done a ton of sit ups the day before. I did use the lortab at home on and off for about a week after.
My suggestion to you would be this. If you have someone who will be watching over you while you are recovering, go ahead and get the prescription from the doctor beforehand but don't fill it. That way, if you decide you do need it you will have the prescription on hand and if you don't need it, you can just destroy it. That way you don't waste the money on something you won't use.
Also, you might see if your doctor offers the on-q pumps or something similar to help lessen the need for narcotic pain relievers.