If you don't know the parrot, I would say no. Even if the owner tells you it doesn't bite, that's no guarantee it won't take a nice chunk out of you. I've had many over the years, from lovebirds to Scarlett Macaws and Blue & Golds and I've been bitten by them all, with one exception. My Goffin Cockatoo has never drawn blood but she has bitten. I have a saying in my house that it's not a bite unless it's bleeding. If you're inclined to touch them anyway, make sure you approach them with the back of your hand and not fingers extended
Also, I thought I should add a few more suggestions. Some people have had to learn the hard way and I wouldn't want that to happen. If you have any non stick Teflon cookware, DONT use them. Even if you see no smoke when you're cooking, Teflon fumes will kill a bird and you could have an avian vet next door and it wouldn't do any good. There is no treatment. Don't give them chocolate, carbonated or alcoholic drinks, avocados, garlic, drinks with sugar, coffee, fresh tomatoes, onions or rhubarb. Mushrooms can cause liver damage. They should be on pelleted diets and given seed ONLY as a treat occasionally. Seeds aren't nutritious and can cause them to get fat. Hope this helps.
Look for guidance and a book or a video or a trainer. Someone versed in feeding a Macaw. My friend had his ulna broken by a Macaw and he knew his way around birds. So, take care, please. Duuuuude.