I would guess more common breeds like rat terrier, toy fox terrier, chihuahua, and jack russel. Even though people are breeding different dogs together to make "designer" dogs I just don't like guessing a breed like Italian greyhound unless they're really common in the area and a lot of people who have them have them unaltered and running loose. If you aren't seeing Italian greyhound puppies (purebred or mixed) in your local papers or on your local craigslist then its probably less likely. Whatever shows up commonly for sale in your area is likely going to be what shows up in the shelters.