I didn't see any Ubuntu repository specifically for using PV-Grub, so I turned to the instructions on Xen's website: http://wiki.xen.org/wiki/PvGrub

Had to install git, get prerequisites for configure to run it's checks, and clone the repository:

apt-get install git
apt-get install python-dev gettext bin86 bcc iasl uuid-dev libncurses5-dev pkg-config libglib2.0-dev libyajl-dev
apt-get install libpixman-1-dev bzip2
git clone git://xenbits.xen.org/xen

The first time I went into the repository and ran configure, libcrypto wasn't found, so it failed.
After searching, and doing a locate libcrypto, I finally found that I needed to create a symlink to libcrypto.so.1.0.0:

ln -s /lib/x86_64-linux-gnu/libcrypto.so.1.0.0 /lib/x86_64-linux-gnu/libcrypto.so

Then I had to install texinfo (apt-get install texinfo) to get past an error with makeinfo. Finally I was able to:

cd xen
./configure
make

and have it complete.

I didn't find the pv-grub boot files in the location given in the documents, but a quick find ./ | grep pv-grub pointed me to the right location: ./dist/install/usr/local/lib/xen/boot/

Next, I copied the pv-grub files to a generally-used location:

cd dist/install/usr/local/lib/xen/boot/
mkdir -p /usr/lib/xen/boot
cp pv-grub-x86_* /usr/lib/xen/boot/

Edited /boot/grub/menu.lst in the guest (DomU):

default 0
timeout 5

title vmlinuz-3.13.0-24-generic
  root (hd0,0)
  kernel /boot/vmlinuz-3.13.0-24-generic root=/dev/xvda1
  initrd /boot/initrd.img-3.13.0-24-generic

then shut it down.

Edited /etc/xen/Guest-A1.cfg on the host (Dom0):

name = "Guest-A1"

memory = 512

disk = ['phy:/dev/Host-A-vg/GuestA1-root,xvda,w']
vif = [' ']

#bootloader = "pygrub"

#kernel = "/var/lib/xen/images/ubuntu-netboot/vmlinuz"
#ramdisk = "/var/lib/xen/images/ubuntu-netboot/initrd.gz"
#extra = "debian-installer/exit/always_halt=true -- console=hvc0"

kernel = "/usr/lib/xen/boot/pv-grub-x86_64.gz"
extra = "(hd0,0)/boot/grub/menu.lst"

Now when I boot the VM, it uses pv-grub.