If I have 2 pawns in a location and I play the Influence card, do I get to place 2 of my influence markers there?

You can only influence a particular location with 1 marker with an Influence action, even if you have more than one pawn at that location. However, the Influence card could be repeated later in that Round, in which case you could add 1x marker again. Controlled Monsters cannot influence locations, so therefore an Influence action can add a maximum of 3 markers to the board, provided all your 3 Pawns are at separate locations.
Related Rule(s)