sounds like some kinda beetle. but without some pictures its just guessing. you can spray you plants with sevin.

If the "yellow bug with hair like a porcupine" is a caterpillar completely covered in long, soft-looking, fur (even its head), it sounds like a puss moth caterpillar (painful and poisonous: don't touch them).

They're usually found on trees and shrubs (their normal food sources), but the one I saw was on a daylily near a lilac.

They come in shades from brown to tan to yellow to white to gray.