I read some of the previous posts to you and some have had some great suggestions for taking safe precautions. (laying it in the sun, spraying lysol and zip up matress protection covers). All of those are great ideas. However, I wouldn't try the bleach method. The ones who scared you half to death, are just trying to be better safe than sorry and no one can blame anyone for that either, but I want to offer a few other thoughts for you and some of those readers.
I too LOVE a good garage sale and getting a bargain. It isn't out of necessity, but rather out of practicality and having fun shopping at them. (hubby and I are financially secure but just have an addiction to yard sales)
Here are some things to think about, when someone tells you oh, I'd never buy that used or let my child or myself eat off of yard sale dishes, etc... or sleep on a used mattress, bedding, etc.... Are those people telling me they have never eaten at a restaurant? You guessed it....... used plates, silverware, glasses, pots and pans, cloth napkins, etc..... Bedding? Never stayed at a hotel? Yep, used mattresses, bedding, towels, etc.... How about if you've ever put your child in dare care? Do you think they buy new cribs, jumpers, swings, toys, bedding for each child? NO, all used by other children and practical. So, what is any difference about buying at a yard sale? When I'm buying something I can see the previous owners, if they look a little questionable in their hygiene I simply don't buy the item. On the other hand, it is fairly easy to see how clean someone is by their home, their grooming, the sale items and their condition and that puts me more at ease. Then of course I always wash, disinfect, and lysol everything before I use it. I'm sure I clean it better than the restaurants, day cares and hotels do. Just something to think about. BTW, they have NO idea what is causing SIDS and they are blaming everything under the sun for it! I raised 2 kids on yard sale cribs, high chairs, bedding, clothes and toys. They are just fine! I'm currently picking up treasures for my new grand daughter and it leaves me more money to spoil her in other ways! Congrats on finding a great deal!