I asked my pediatrician about that and she said in her experience, she had never met a bilingual child who wouldn't have what would be considered a language delay in a monolingual child. She said that she doesn't put a lot of stock in research to the contrary and that the jury is still out on the issue. I find so much conflicting information about it, I tend to agree with her.
Well, she's entitled to both her opinion and her experience
The research I've seen is fairly convincing to me (and I am a linguist so the methodology that has been used is something quite familiar to me, although I do not specialize in language acquisiton). And as far that goes, I don't think the jury is really out at this point.
Of course, there is anecdotal evidence both ways. And if it seems like I'm totally contradicting myself right now, I will nonetheless admit that my bilingual dd seemed a little slower in starting to speak initially than some of her friends: she didn't really start talking much until about 18 months old when she had a language explosion and basically caught up to and even surpassed the language skills of most of her peers seemingly overnight--and I don't even think she was ever really to the point where she would have been considered "speech delayed". 18 months isn't really THAT old to start talking, even among monolingual kids
Further, I don't necessarily think she would have started any earlier had she been monolingual. Actually I do know another bilingual child of the exact same age as dd (they were in the same daycare group) who started speaking in sentences by the time she was about a year old in both English and German. So who's to say?
It is an interesting question, though, and I actually did an informal poll here on the issue:=895649
So MDC anecdotal evidence also supports the lack of delay among bilingual children with the majority of respondants indicating that their bilingual children were either always on par with their peers verbally, or ahead of them. Obviously FAR from scientific, but if one wants to reject the current research and make conclusions anecdotally, this should qualify as much as anything else. And, by the way, I personally DO believe that anecdotal evidence counts for something. Isn't there even a saying along the lines of "research is just anecdotal evidence that's been peer reviewed"
Anyway, as I said, it certainly runs both ways on this issue (look at the number of people on this thread alone who say that their bilingual child is behind in speaking!)--but based on that very diversity, I think it's hard to make a blanket statement that "all/most bilingual children start speaking later than their monolingual peers." At best one could state "Some bilingual children start speaking later than their monolingual peers." But based on other statements (such as the ones in the poll thread), it is equally possible to state "Some bilingual children start speaking earlier than their monolingual peers."