Home Depot, Lowes, or any other similar hardware store. Think about it, who the hell is going to be at home depot during an infection? Granted, there might be some people there, which is why you lock it down and start a slaughterfest on any zeds inside. The sheer amount of building materials at your disposal makes fortification simple. In addition to that, the tools and supplies make great weapons, and allow you to make greater weapons and traps. Finally, the gardening section of these places allow you to grow your own food on the roof when you run out of scavenged products. Forklifts, rider mowers, generators, and other heavy machinery have many applications for survival as well. Hell, you could probably tunnel your way to a Walgreens, or Safeway or something from a home depot. Preferably in a state where the climate gets below freezing. Frozen zombies. Hehehe.
I would gather the needed supplies and move our group (core group is 3 families-15 people, 9 who can shoot, 3 who can load) up to the top of a steep hill near our home, only 1 access road with a clear 360 degree view. We already have livestock and gardens, there would be enough room to set up rv's and defenses. Only the road itself is easily negotiated on foot and only about 12 ft across. A nice bottleneck that could be squeezed a bit more with minimal construction. My brother has a couple of ultralights, if we needed to gather some extra supplies.
Directly to Wal-Mart. You could easily shore up the entrances and loading docks.. Plenty of non perishables. Guns , ammo and camping supplies along with anything else you could possibly think you may need.. One could stay here for very long periods of time and bring in other non infected people. Wal-Mart also has a very well stocked pharmacy...