I am trying to get a % of where we are at with Release A. I can get a % of where we are with each epic, but I don't see a % of the release as a whole. Does portfolio show you a % complete by Release?
Similar to the epic progress bar that can be added as a column in the scope view of a plan, you can see the progress bar for the releases in the release report, as covered in "Using the releases report".
However selecting the Release does not show a % complete similar to the Epic Progress does from the scope pane when you click on the progress bar field. To dig further into the release itself you can select the "View Version" link from releases page:
This will take you to the release page for the release details as covered in "Using the release page to check the progress of a version"