There's a Target on Hwy. 278 in Bluffton...you'll see it on the right as you approach the island. (But I'm not absolutely sure it's a Super Target, you might want to double check on their website, my recollection is that they have many grocery items but not the whole shebang with produce, etc.) They are in the process of adding a stoplight on the other side of the street and my guess is that it will also cut through for access to the Target as well. Otherwise, keep your eyes peeled for the sign...if you pass by it make the next right into a car dealership (BMW? Saab? something like that) area and you can cut back through the parking lot to the Target. It's difficult to make a u-turn in that area.
There's also a Super Wal-Mart closer to the I-95 on 278, or a regular Wal-Mart on island.