Another issue with Walmart bikes, it may be some old retired guy assembling it that actually knows how to use tools or it could be an 17 year old that doesn't know metric from sae wrenches.
I have bought a couple of bikes from bikesdirect and I am happy with them. I'm an old man but the dawes would work if you want new I would change it to a 20 tooth cog on the back. If I am on a budget I would watch market place and Craigslist. It been a few years back but I bought a like new Surly Steamroller for $300 lots of good bikes for less than that.
If I didn't already have 8 bikes there is a old steel Raleigh C-30 in great shape on marketplace now that I like (I'm trying to ignore it) it's not a single speed but would be a good commuter