It only makes sense; if this is going to be where they'll be living for the foreseeable future, they need to know the area, and they also need to have supplies so they can keep on living. He's still working on the food situation, but exploration is more his thing anyway. It keeps him active and gives him something to think about.

He doesn't notice Steve right away, because his attention is on scouting out this area, but eventually, he realizes he's not alone any longer. When he hears Steve's warning shout, he turns and he does a double-take. Obviously he recognizes Steve, but he's also not the Steve he remembers seeing last.

"Hey, man. They got you too, huh?" He can't be sure what the other man remembers, but judging from his appearance, he figures maybe he hasn't yet encountered Thanos. "Of course I know you. Captain America, Steve Rogers: the man with the plan." And honestly, Clint's just relieved to see him.