Re: I guess daycare wasn't the right choice for us. :(
Any child that goes from staying home to being around other kids a lot will get sick a lot in the begining. It can happen now, or it can happen when he starts school. As for letting sick kids in, if they kept every kid out with a runny nose, kids wouldn't be there more than half the time. My sitter doesn't allow kids with temperatures or who are vomiting, but just a runny nose or a cough - if she kept my dd out every time she had a little cold, I'd be home from work more than I'd be at work. Kids have to build up immune systems at some point, kwim? When I started teaching I was sick *every* week almost - I caught every little bug. Now I have an incredibly strong immune system.
It doesn't sound like that great of a center, though, from your description of the caregivers. It might be better to enroll him in a real preschool program a few mornings a week rather than an actual daycare. That way he's around teachers, not teenagers, and building skills for school, and will still get the stimulation he needs and interaction with others.