I would advise against it. In my experience, angelfish need a lot of space to live together. The trouble is that they are aggressive and territorial, but also extremely social. It's a weird combination. I have five fully grown angelfish in my 150 gallon and they get along great because they have plenty of room to get away from each other before conflicts get out of hand. The tank is also well planted and has lots of driftwood to hide in.
I kept a group in a 30 gallon once, and as they grew up I had to rehome all but one of them. The dominant individuals constantly picked on the others, who had nowhere to escape. The one I kept stayed healthy, but he acted bored (at risk of anthropomorphizing). I don't think I'd keep a group of angels in anything smaller than a 75 gallon tank again, and I wouldn't want to keep one alone.
Predation on neons is a real issue. If you get the angels as babies and they grow up with the neons, it can work. But it might not. Some angels are more predatory than others. I like to keep angels with the chunkier-bodied tetras, like rosies, phantoms, lemons. They are too tall to fit in the angels' mouths. Angelfish are intelligent enough to figure this out pretty quickly, and then they leave the tetras alone.
