According to TVbytheNumbers.com, "Dead Men Don't Wear Plaid" had 2.924 million viewers in its first half hour, and 2.855 in its second half.
"Returning with new episodes, the CW’s Vampire Diaries scored a 1.5 adults 18-49 rating, that’s the same as its last new episode (2/11). Vampire Diaries was down 8% to a 2.2 rating in the CW target women 18-34 demo. Supernatural’s 1.2 adults 18-49 rating was up 20% from its last original episode (2/11). Supernatural was up 8% in the CW target women 18-34 ratings to a 1.3 rating."