Angelfish will eat most things that fit in their mouth. So the guppies will have to be bigger and the angelfish smaller. But long term it's not a good idea.
Not a good idea. Male guppies are certainly bite-size from the perspective of an adult angelfish, and there are numerous reports of angelfish pecking at the tails of fancy guppies even if they don't eat them outright.
That said, I've kept female guppies in community tanks with angelfish, and the angelfish generally ignore them (though they do eat the fry).
If you get LARGE guppies while the angelfish are SMALL than maybe its a posibility- but there is a good chance that the guppies will become snacks when the angels grow to full size.