I've got a pile of old blinds left behind by tenants who chose to put up new blinds instead of living with the curtains provided in the suite. If you're willing to pay for the packing and shipping, and fill out the necessary declaration forms for your US customs, they're yours for the asking.
Generally, tenants who put up blinds did so in order to cut down on the radiant heat from the Sun coming through the windows. Metals, even the thin metal in Venetian blind slats, are the most opaque materials known to man. You can stop more light with a piece of aluminum foil than you can with any other material of equal thickness. And, that's not just true of visible light; it's also true of the entire electromagnetic spectrum. (although I'm not entirely sure if radio waves can penetrate through metal) So, by putting up metal blinds, you can greatly reduce the amount of infra red light (or heat) that comes in through your window.