Well, HP's support site lists an E709a, E709n and E709q, but I looked through the online installation instructions for all 3 and none of them say you can install via ad hoc... they all have instructions for installing via access point, though.
I see the manual DOES say you can install via ad hoc, but perhaps its author was mistaken.
So I would install the drivers and software and temporarily connect the laptop to it with a USB cable when prompted, then switch it to wireless using the instructions at
http://h10025.www1.hp.com/ewfrf/wc/document?lc=en&dlc=en&cc=us&product=3944627&lang=en&docname=c01624891You should have the Firewall enabled while installing, by the way, so the setup program can open necessary ports and add its programs to the trusted list. If the firewall is disabled during install the setup program may assume those changes don't need to be made.