Unfortunatley there are very few (better said, no) lenses that meet your criteria. A proper wideangle zoomlens is hard to find for anything under 600 dollars, I'm afraid.
I'll sum up the few options you have :
- Sigma 15-30 3.5-4.5 EX Asf. DG : (+- 550 dollars)
A very popular wideangle zoom, which is ruggedly built, has a low price, and goes very, very wide. Distortion can be kept to a minimum by avoiding the far tele and far wide, although perspective distortions can be very charming in extreme wideangle shots.
- Canon EF 20-35/3.5-4.5 USM ø
Another wideangle, albeit not as extreme as the sigma one.
I cannot speak for it, since I have not used this or tried it before. It's price should be something around 500 dollars.
Well good luck in your choices!