Can I watch High Definition video without a blu ray player?

Yes you can.

If you mean cable as in the broadcast feed from a cable supplier, then Bluray player operates independently of the broadcast feed.

If, by high def cable, you mean the cable from the player to the television, it would be an HDMI cable. Even without an HDMI cable, almost all Bluray players have a composite video interface that will deliver a standard definition version of the output.