Not really, they were already shooting at you already at +5, from your position you will be firing back at a -5 and to do so you will have to place yourself in the open (note what Wanderer did). I wanted to give you a choice before I continued.
Yes, both sides are shooting and I calculate two attack rolls for each character (one for either side). Hiding on one side means just one attack roll against a character.
We will all join Wanderer along the side of the mountain to spare us from two attacks by archers. We will continue to shoot at the archers we can see. We will ready weapons to face those on horseback. We will use arrows on the horsemen until they start to get too close.
Wanderer gives our response by shooting at the speaker with her bow while the rest of us shoot arrows at the other riders. We will welcome a fight with them and We believe that we can win. We will switch to melee weapons as soon as those on horseback close with us. If they stay back we will continue to shoot with arrows at the horse and any archer who shows himself on the cliffs.