Spoiler:
^I thought about that but I figure Ray didn't have many options at that point. He was out of gas because he was trying to buy time for Ani, he obviously couldn't escape, he could have gone to a public place where they likely would have just shot him on sight, or he could do what he did and go to nowhere.
I guess when he knows that he is going to die, he might as well go somewhere public and use the cell service for the message but by going to the forest he at least had an opportunity to get revenge on Burris. If he killed Burris in a public area that had cell service and sent his message, he would be all over the news with footage of him killing a cop. At this point, everyone thinks he's corrupt but the L.A. Times reporter could release his story and clear his name posthumously.
The part that got me was when VV died in the desert and when Ray almost told Ani he loved her, he finally got to be happy for a bit with that and seeing his son treasure his badge (or trade it for trading cards, who knows).