I think a speech delay is where a child's speech develops in the normal way, but slower than other children (a 'late-bloomer'), whilst a language delay/disorder is where a child's speech develops abnormally, resulting in difficulty communicating.
For example, I didn't speak for longer than is normal (and apparently didn't cry as a baby), but when I did my speech was very fluent, and I picked up native and foreign languages more proficiently than other children. My brother always teases me because I can speak many languages, but I hardly speak to anyone at all, even in English.
So, I had a speech delay. I sometimes wonder if I don't have a language disorder too though, albeit a beneficial one, because I clearly learn languages differently to other people. I see patterns in them and attach strong visual imagery to words. I often dream in other languages (my mother also claims I often spoke a Russian-sounding language in my sleep as a child ). Interesting topic.