Well, it depends. I personally have 2 angelfish and 12 neons living together in a 30G tank. My angels never ate any of my neons. I believe this is because they were all raised together. I bought my angels when they were still very small (about quarter-sized), and I bought them together with neons. This way, they grew up together with neons, and they don't bother them at all. They're used to neons and they're fully grown angels now of about 5-6" tall (with fins taken into account; without fins they're about 3-4"). So, if you get neons and angels while angels are still small, they'll get used to neons and won't bother them. However, when you add adult and fully grown angels, who never lived with other small fish, to a tank with smaller fish - there is a good chance the angels may eat the smaller fish.
Well, like Isabella said, it all depends. In some cases, the Angelfish, and Neon Tetras will get along, but a fully grown Angelfish MAY just look at a Neon Tetra as a snack. If you want to, you can take the chance, but it wouldn't be smart. All up to you. ;D
yup I agree though angels won't eat full grown guppies as you see mine don't eat my guppies and if you do what Isabella did you might be fine it depends on your angel as I have read that some angels will eat there neons or cardinal tetras while other people like Isabella are fine and yet other people have told me that they were fine for a couple years then randomly the neons disapeared (angels were the culprit) but if I were you I would buy the neons first let them get full grown and used to the tank and then get a few angels depending on the size of your tank but just so they won't be crowded and feel like eating the neons and keep your angels well fed