These are probably Seville oranges, which were developed to be bitter for use in cooked dishes.
The best use I've found for them is marmalade. They make an incredible marmalade.
There are also commercial brands of Seville orange marmalade available, so you might buy a small jar (maybe at upscale grocery stores?) for taste-testing before starting to wash and chop your Sevilles.
I absolutely adore Seville orange marmalade, but it's not a universal admiration.
Sunset Zone 17, USDA Zone 9