Yes you can - via email, a cloud service like DropBox or by using the iOS feature of file sharing. In order to save and/or edit the document - other than if you save the email that contains the file - you will need a third party app that is compatible with Excel files such as Apple's Numbers app, Documents to Go, Office2 HD etc. and others that you can find in the app store.
On the iPad, files are stored directly in the compatible app in which they can be edited or created. So the Excel file would be saved in one of those compatible apps. If you email, the file - just save the email until you make the decision on which app is right for you.