hi,
my DD is 2.4 and says about 14-15 words and that's it. absolutely fine in all other ways, no concerns at all.
her lack of speech has been concerning me for ages and i approached the HV about it - she had an assessment y'day morning and in all other areas apart from speech, she is 6-8 months ahead of where she should be.
even though she says few words, what the HV was looking at more than anything was her understanding, which is outstanding, and whether the words she does use are said with meaning and appropriate, which she said they were, i.e. door when she sees a door type of thing.
what the HV said was some DC are thinkers and stand on the sidelines taking it all in and actually know more than they let on, others are like a bull in a china shop and jump in with random words etc that don't really mean anything. apparently my DD is a thinker...which did make me giggle.
also, like yours, she was an early walker (10 months) and physically she is way ahead....it really is true, they can't be good at everything and when i said about other 2 year olds having conversations with you, she said can that may be but can they do other things that DD can - my friends DD who is a week older is an amazing talker, but she can't run very well, still can't walk up or down stairs and only starting walking at 23 months...kind of puts it all into perspective.
i have to say it put my mind at ease like you wouldn't believe - i was so upset and worried about her lack of speech it was keeping me up at night - today...literally...she came out with 3 new words, i was so shocked and proud i could have cried.
easier said than done (coming from the world's biggest worrier) but please try not to worry too much about this, she is still so young and has PLENTY of time to catch up (not that she's even behind but you know what i mean lol).
it was only when i kind of thought to myself that i should stop worrying myself about what DD isn't doing and acknowledge what she can do, that i realised she ain't half clever my little girl 
xx