Can I upgrade to OSX 10.9 and format my HD along the way? I want to upgrade from ML to Mavericks but I want to erase and format my HD to a single partition along the way. Is this possible?
Yes you can use disk utility to reformat the Macintosh HD partition during the installation of Mavericks, however if you want to create a new partition using disk utility the you will have to create a Mavericks install USB so you can boot from there. 

You can't create a Partition when booted from the same drive hence the need to boot from a USB installer. 

Creating a USB installer is as follows, Format the USB thumb drive as a Mac OS Extended (Journaled) and name the USB thumb drive Untitled

Download Mavericks from the Mac App Store,

Copy and paste this command into terminal,

sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Mavericks.app —nointeraction