We were just there this evening! It is on 192 on the LEFT if you are coming from the WDW area (I4) It is just past where 535 - Vineland road meets 192.
An easy way to the SAM's Club--Take Hotel Plaza Blvd; turn right onto 535. Take 535 all the way to 192; turn left onto 192; SAM's Club is just a short ways up on your left. We go there all the time--it's not a long drive. To get to the Super WalMart, you have to pass SAM's and keep driving down 192 for quite a while.
Thank you so much, it's easier to buy supplies there than to pack the car down. We shopped at Walmart last time but for an 11 day trip, I would prefer to buy snack food at Sam's.