Unfortunately, there isn't a single page from which you can export all of these details. You can extract the Portfolio item details by adding the desired columns to the Track > Portfolio Item page, then using the export option from the Actions button. This will create a .csv file with this information. You can change the type of Portfolio Item on the page to export each type.
To export information on the child User stories to the Portfolio Items, you can go to the User Stories page and create a custom view which contains the fields you want included. To create a custom page, click the New Custom View icon on the Plan > User stories page. The New Custom View editor opens - enter a name. To show the stories that have a Portfolio Item view, you can use a condition which is Feature != No Entry. Select which columns should be displayed and in what order. Once you save the view, you can use the Export option from the Actions button.
Another option for exporting this data for reporting would be to use the Excel 2010 Plugin.
The Rally Add-in for Excel provides a quick and easy way to import or export data from your Rally subscription for tracking, reporting, or sharing. The data can be organized in a pivot table or displayed using Excel's built in charting capabilities. Multiple Rally object types can be imported from or exported into multiple worksheets and the data cross referenced for more complex needs.
The plugin can be found here (the download link at the bottom):
http://www.rallydev.com/help/rally-add-excelThe Installation & User Guide is here:
http://www.rallydev.com/help/rally-add-excel-installation-user-guide