With younger kids, I guess I try to remember that these little things are not strictly measures of intelligence. I think if you can truly strip that supposition away from your thinking, it will be evident in your exchanges with other parents.
As opposed to saying, "I think she is gifted," or even thinking this when someone asks about her signing, I would laud signing and the program itself for giving your daughter a way to communicate before she is ready to talk. You can comment on our print-rich environments or how our culture emphasizes early learning right now. Personally, I have come to believe that learning ABCs is about interest and exposure. If it is not letters it would be something else. Toddlers love to learn! Also, early motor skills can be about personality. Attention spans can be about temperament, etc.
That is not to say you can not brag and be proud. But, when you truly feel that every time your DD does something better, faster, or more than her peers it is because she is more intelligent, than those feelings are going to keep you from connecting with other parents.
I think there are definitely times and places to be blunt about it. This place is one. I am way more specific here than anywhere else, because...that is why we come here, right? But, I think you do your child a huge favor when you stop seeing everything they do as evidence of their intelligence, and look at them in a grander scope. Gifted our not, every child is a unique and complicated individual, and not everything they do boils down to an IQ number.
I think if you keep some of this in mind, be honest, and remember that you cannot control how someone else is going to think, you will be alright.
