It's fine to substitute canned beans for dried, but keep in mind that the sodium in canned beans is higher than that of dried. You can reduce the sodium by about 41 percent by rinsing and draining the canned beans, but even then, you might want to decrease the amount of salt in the recipe.
Also, some major brands, such as Goya, are now making a line of reduced-sodium beans. And organic canned beans tend to be lower in sodium than regular grocery store brands, so read labels.
Here are some substitution amounts that may be helpful:
1 pound dried beans (about 2 – 2 1/2 cups) = 4 1/2 – 5 cups cooked beans
1 cup dried beans = 2 – 2 1/2 cups cooked beans
1 (15-ounce) can beans = 1 3/4 cup – 2 cups