If you feel wary, then of course DO NOT give them any information or allow for them to adopt your cats. Always go with your gut instinct when it comes to these things. I know there are sick people out there who will "buy" your "pet" and then turn around and use them as bait for Lord knows what, or other similar things.

So I would maybe reply and request some more information from them (such as, location, reason for adoption, what their lifestyle is like etc) and if they don't reply or seem really annoyed in their reply then I would write them off for good!