A lot of birds like going everywhere with their owners. Just some things to consider though:
1. Does the friend have dogs/cat, and if so, will they be willing to put them outside/kennel them while your bird is there? If not, it is NOT worth the risk of your baby being injured or killed by a larger predatory animal (and no matter how "nice" a dog or cat is, if it's not used to bird, it see them as a play thing or lunch). Not too long ago, someones conure got eaten by a dog when the owners weren't paying 100% attention for just a few minutes.
2. Do you have a cage or carrier with food/water dishes? A short walk on your shoulder may be one thing, but a bird who will be away for several hours needs food and water provided, as well as a safe means of transport. A harness is not sufficient for a longer time period away from home.
3. Is the friends house otherwise conducive to your bird- i.e. no smoking indoors, no drugs or excessive alcohol being used there (things that could impure judgement and lead to your bird being injured/killed), no teflon/non-stick pans, doesn't use excessive air fresheners/candles- you know, things that other people may not know are dangerous to birds or situations that may put your bird in danger.
So long as its a safe place for you bird to be in, I see no problem. Many birds enjoy traveling and "seeing the world", and it is actually very good for them mentally to get out and about
Wanted to add, our bird has come many places with us. The only friends house who I was leery of bringing him to (and never did) had a cat and smoked inside. But he came to my parents house, as well as to other relatives, and we had several neighbors who were just thrilled when Kiwi came over to watch a movie or something. He always came in his travel cage, which he could stay in or was allowed to sit on top of. He was never really allowed to wander in other peoples homes though, too many dangers in a non bird-proofed house, plus if he pooped or chewed, that would not be good!