Elasticsearch Array (Label/Tag Querying

I really think that I'm trying to do is fairly simple. I'm simply trying to query for N tags. A clear example of this was asked and answered over at "Elasticsearch: How to use two different multiple matching fields?". Yet, that solution doesn't seem to work for the latest version of ES (more likely, I'm simply doing it wrong).

To show the current data and to demonstrate a working query, see below:

{
    "query": {
        "filtered": {
             "filter": { 
                 "terms": { 
                    "Price": [10,5]
                }
            }
        }
    }
}

Here are the results for this. As you can see, 5 and 10 are showing up (this demonstrates that basic queries do work):

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 6,
    "successful" : 6,
    "failed" : 0
  },
  "hits" : {
    "total" : 4,
    "max_score" : 1.0,
    "hits" : [ {
      "_index" : "labelsample",
      "_type" : "entry",
      "_id" : "AVLGnGMYXB5vRcKBZaDw",
      "_score" : 1.0,
      "_source" : {
        "Category" : [ "Medium Signs" ],
        "Code" : "a",
        "Name" : "Sample 1",
        "Timestamp" : 1.455031083799152E9,
        "Price" : "10",
        "IsEnabled" : true
      }
    }, {
      "_index" : "labelsample",
      "_type" : "entry",
      "_id" : "AVLGnGHHXB5vRcKBZaDF",
      "_score" : 1.0,
      "_source" : {
        "Category" : [ "Small Signs" ],
        "Code" : "b",
        "Name" : "Sample 2",
        "Timestamp" : 1.45503108346191E9,
        "Price" : "5",
        "IsEnabled" : true
      }
    }, {
      "_index" : "labelsample",
      "_type" : "entry",
      "_id" : "AVLGnGILXB5vRcKBZaDO",
      "_score" : 1.0,
      "_source" : {
        "Category" : [ "Medium Signs" ],
        "Code" : "c",
        "Name" : "Sample 3",
        "Timestamp" : 1.455031083530215E9,
        "Price" : "10",
        "IsEnabled" : true
      }
    }, {
      "_index" : "labelsample",
      "_type" : "entry",
      "_id" : "AVLGnGGgXB5vRcKBZaDA",
      "_score" : 1.0,
      "_source" : {
        "Category" : [ "Medium Signs" ],
        "Code" : "d",
        "Name" : "Sample 4",
        "Timestamp" : 1.4550310834233E9,
        "Price" : "10",
        "IsEnabled" : true
      }
    }]
  }
}

As a side note: the following bool query gives the exact same results:

{
    "query": {
        "bool": {
            "must": [{
                "terms": {
                    "Price": [10,5]
                }
            }]
        }
    }
}

Notice Category...

Let's simply copy/paste Category into a query:

{
    "query": {
        "filtered": {
             "filter": { 
                 "terms": { 
                    "Category" : [ "Medium Signs" ]
                }
            }
        }
    }
}

This gives the following gem:

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 6,
    "successful" : 6,
    "failed" : 0
  },
  "hits" : {
    "total" : 0,
    "max_score" : null,
    "hits" : [ ]
  }
}

Again, here's the bool query version that gives the same 0-hit result:

{
    "query": {
        "bool": {
            "must": [{
                "terms": {
                    "Category" : [ "Medium Signs" ]
                }
            }]
        }
    }
}

In the end, I definitely need something similar to "Category" : [ "Medium Signs", "Small Signs" ] working (in concert with other label queries and minimum_should_match as well-- but I can't even get this bare-bones query to work).

I have zero clue why this is. I poured over the docs for houring, trying everything I can see. Do I need to look into debugging various encodings? Is my syntax archaic?