I have to say that some of that sounds perfectly normal for an 18 month old. Even though DD signed very well at home for a long time and speaks well now it wasn't until a month or two ago that she actually started speaking to other kids (so around 20-21 months old). She still doesn't speak much to other kids but will happily speak to adults (although not nearly as well as she does to myself or DH).
Also, she's always had pretty bad separation anxiety. She's in daycare for two weeks starting today and I was SHOCKED that we didn't have a full-blown tantrum (but am expecting one tomorrow). We still have tantrums if I go to the bathroom (or DH sometimes).
The wandering around does sound a bit odd... DD is normally pretty involved with toys (or playing with other kids) so maybe somebody else knows about that? It could just be a personality thing but I really can't say. But I don't think other kids not responding to her would make her not engage with the toys there. If anything you think she would want to play with them more?
