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I'll look at the page from a technical standpoint.  You may or may not have the ability, resources or time to make these improvements, but here are my thoughts:

• There are too many HTTP requests being made (83 I think) and the page load time suffers (for me between 3 and 12 seconds).  Looks like lots of Javascript files that may not necessarily be used on this particular page.  The scripts are pretty small in size, and your images seem to all be optimized for the web also - so that's good.
• You have rel="nofollow" on your own top navigation bar (My Account, My Cart, etc) and in other parts of the page.  Is there a reason for this?
• Images don't have alt text.  This would definitely give you a boost in image search.
• Responsive Design is missing.  Not sure how important it is to your target customer base, but it's becoming increasingly important.

Listings like Yelp have continued to increase their traction in SERPs in the past few years.  Yelp is a very trusted source of information, especially on a local scale.  Broad-match keywords like "local diners" will most likely give you Yelp or Google Places results, as opposed to individual websites.

When considering SEO, most people will focus their efforts on driving organic search traffic to their site.  Really though, we should consider our online reputation as a whole.  If you get a customer to walk in your front door, does it really matter if they found your webpage, or if they found you on Yelp or FourSquare?  As marketers, our ultimate goal is to generate leads and convert them to sales - it does not matter how we reach the end result.

So in short - you shouldn't be alarmed by this, and shouldn't even feel threatened by it.  Use these platforms to manage your online reputation, receive feedback, and engage your potential customers.

The number of categories you have on your WordPress blog should accurately reflect the content you write about.  If you have a legitimate need for 50 categories, then by all means, 50 categories it is.  If your content all falls under 5 categories, then that is all you should need.

Essentially, let your content dictate how many categories your blog has.  Remember to look out for duplicate content, or pages with little to no content.  It's possible that you have a single blog post that is tagged to two categories - and those categories have no other posts attributed to them.  The category pages will then show short excerpts of the content (little to no content), and be essentially identical because the same post is tied to them (duplicate content).