My mom loves having hostas around the yard, and garden, so I was wondering if all of them are edible, or just some of them.
Seems they are - they belong to the Asparagacaea family, and are apparently eaten frequently in Japan and other countries. As with many food plants, the young leaves are best - older leaves can become tough, stringy and bitter. Some varieties are used more commonly than others as vegetables, H. seiboldii and H.montana, but they can all be eaten. They'll behave like a cut and come again crop, producing more leaves to replace those you've cropped. More info here
According to Wikipedia info, all hostas are edible. But do not trust me or Wikipedia blindly.
In any case, I would not eat it too much and too often.