Neon and cardinal tetras should be added to a tank after it has been well established for about 2 months. This is becuase they are very sensitive to water conditions (ammonia & nitrITEs).
Neons and angelfish should be fine together for awhile, until the they (angelfish) get bigger and the neons stay relatively the same small size. Don't forget angelfish will grow to about 6", while neon tetras will stay to about 1.5". So even they have been growing up together, with the large size of the angelfish, the neons will look very tasty to them. Cardinals will grow to about 2".
The general rule is, any fish that can fit in it's mouth, will.