There's clearly nowhere for them to go. If they stay on the road, they'll be eaten. If they run into the jungle, they'll probably catch some kind of awful tropical parasite. And then be eaten.
Cut To ...
Oh, wait, no: They can climb down this sheer cliff face, which just appeared out of absolutely nowhere.
Using deluxe Climbable Fence Cables.
And we say "appeared" because it literally appeared there during the edit between those two scenes. The tyrannosaur breaks through the fence, then the heroes crawl through the broken fence the dinosaur just burst through, only to find the concrete wall you see above. How in the hell did the dinosaur scale that? With its tiny little T. rex arms? Hell, the only reason hiding down there works is because the T. rex can't chase after them. Is it like when a little kid climbs up a tree and then is too scared to get back down?
We'd say it flew up there, or jumped, but we actually see it standing on the other side of the fence -- on the ground that, one minute later, we see doesn't actually exist:
Seriously, is it up in a tree?