Of course I am! I love everything about my sun sign! Okay well maybe not everything but most of it. ^_^;;
I don't think there is anything to proud or not proud of. This implies that a sign can be inherently good or bad. It is what it is.
I really love being a Cancer. I think its one of the best signs, and I fit it perfectly. Maybe not, but there are traits you could be ashamed of. For instance, Cancers can be moody and emotional, Libras shallow and fickle, Virgos prudish and critical, Aries hotheaded, Pisces dreamy and impractical... I'm still proud though, I'll take the good with the bad.
Of course i'm proud of my sign. Because as i read about the qualities of a person that has this sign it really describes my personalities. I'm proud for being a LEO!