I am not aware of a way to set speakerphone as the default, but you can check the User Guide and see if anything there helps. http://manuals.info.apple.com/en_US/iphone_user_guide.pdf
In checking, the only thing I can find about Accessibility and calls has to do with incoming calls, not outgoing. You can set the speaker as a default action for incoming. I don't know if that will carry over to outgoing, but I suppose that you can test that yourself.
Message was edited by: ChrisJ4203
Lock the screen in portrait orientation: Double-click the Home button, swipe the multitasking bar from left to right, then tap icon with the circular arrow in a square. Read this http://support.apple.com/kb/TS3805
To make calls using voice dialing have Siri on and set in settings/general/Siri/raise to speak to ON