Allos' are like land sharks. They can see you from a mile away, travel in packs, and are extremely fast. Chances are if you can see it, it's too late for you if you're on foot.
Best chance for survival is find another Dino and run beside it to try and get agro off yourself
THE best way to tame anything is to use an argy cage, simply use like 5 dinosaur gateways made of stone and keep one gate door open before you find a dino to tame, once you do, lead it to the cage and then run out through one of the gaps between the gateway frames and obviously close the door and, tadaa, one stuck dino to tame