If your background color is not used OTHER than background, just remove that color. If it is used elsewhere, you may have to do it in pieces or replace the missing spots resulting from a global remove color.
If the background color is NOT used elswhere, removing the color from the palette will remove all of them at once. You will receive a confirmation message of the number of stitches to be removed. Just approve it from that point and POOF! All the background is gone!
If it is used elsewhere and you do this, you need to add it back to the palette and put those stitches back in manually. If you use highlighting, you can tell if there are stitches other than background to do it.
If it is used in the design itself and it is too cumbersome to put them back manually, you can mark sections of the patter avoiding those stitches and just remove from the area. Keeping highlighting turned on in this case is a good idea.