I know how you guys feel. I dont have a garage either. I bought a Budge Lite Semi-Custom Car Cover from Walmart. It was $25 dollars i believe, and you need to get the "Size 3 Fit" (fits cars to 16' 8" in length).
It works great and has the following features:
Spun-bonded Polypropylene
Breathable
Water Repellent (not water resistant, big difference)
UV Treated
Double Stitched seams
and much more.
It doesnt come with a lock system (just a shoe lace string size rope that ties it down) but its not a big deal because the car cover fits perfect and is elastic so it doesnt need any lock unless you think someone will take the time to steal your car cover, then you can buy the lock for it by mailing the registration card plus $10 dollars and they will send you a lock kit.
All i had to do is cut a small hole after i put on the cover for the license plate to show and that was it, oh i also made a hole for the antenna (they have a kit with the system for the antenna hole). Well, i enjoy the car cover and at only 25 bucks you really cant loose, it keep my car clean and any bird droppings and harsh sun off of it.