I do but it depends on the situation and how approachable they are. If someone is walking by or is engaged in conversation or something I won't pursue them. But if someone is engaging with me or in an aproachable situation and has really nice curly hair, I'll say something.
Only a couple of times have I asked how someone got their curly look. One time it was asking who cut a woman's hair and that worked out great; I went to her hairdresser with excellent results. The other time I asked about products and the results I got weren't as good as hoped.