You don't need a Cablecard to receive local HD channels if your TV tuner has QAM support. Look in your manual to see if it says anything about the tuners, like NTSC/ATSC/QAM or something like that.
Just try connecting your TV to the cable and have it search for channels. It costs nothing but a little of your time. If it can't receive the unencrypted HD channels THEN look into the other options.
In my market, the cable company absolutely will not give you a Cablecard unless you subscribe to a digital package.