I got stuck here as well. It seems like you want to go up but you actually have to go underground. Follow the path at the bottom right corner of the map, starting from the bottom entrance, and you will go underground, where you can curve around to the left and head towards the waypoint.
Finally found it after 2 minutes after posting this -_- Then I keep getting my ass kicked fighting some mini boss on a later quest and rage quit. --- http://i.imgur.com/ywEXn.gif http://i.minus.com/ibm3Ti5mZYdMON.gif http://i.imgur.com/ZYPIO.png
I just gave up on this quest after getting destroyed multiple times by a bunch of guys who set me on fire. I need to find some new ranged guns, mine all do fire damage and do no damage to those guys and when I get in close with my OP shotgun I get burnt.