The ad sounds good to me, but we ARE talking about the general public. Think about it: it says spay/nueter right in the ad, so why did they even call to say "I don't want to pay for spay"? Because people are STUPID !!!

How about:
Rescued, stray cats in need of a loving home. Patience and understanding is mandatory while cats adjust to their new surroundings. Spay/ neuter and adoption fee required.
Indoor homes only. Serious cat lovers need only apply. NAME at PHONE NUMBER.